MAC. SKE in Practice. Lecture 5


 Kelly Ryan
 2 years ago
 Views:
Transcription
1 MAC. SKE in Practice. Lecture 5
2 Active Adversary
3 Active Adversary An active adversary can inject messages into the channel
4 Active Adversary An active adversary can inject messages into the channel Eve can send ciphertexts to Bob and get them decrypted
5 Active Adversary An active adversary can inject messages into the channel Eve can send ciphertexts to Bob and get them decrypted Chosen Ciphertext Attack (CCA)
6 Active Adversary An active adversary can inject messages into the channel Eve can send ciphertexts to Bob and get them decrypted Chosen Ciphertext Attack (CCA) If Bob decrypts all ciphertexts for Eve, no security possible
7 Active Adversary An active adversary can inject messages into the channel Eve can send ciphertexts to Bob and get them decrypted Chosen Ciphertext Attack (CCA) If Bob decrypts all ciphertexts for Eve, no security possible What can Bob do?
8 SymmetricKey Encryption RECALL SIMCCA Security Send Recv Key/Enc Key/Dec SIMCCA secure if: s.t. Replay Filter REAL IDEAL IDEAL Env Env REAL
9 SymmetricKey Encryption RECALL SIMCCA Security Invalid ciphertexts are silently ignored Send Recv Key/Enc Key/Dec SIMCCA secure if: s.t. Replay Filter REAL IDEAL IDEAL Env Env REAL
10 SymmetricKey Encryption RECALL SIMCCA Security Send Recv Key/Enc Key/Dec SIMCCA secure if: s.t. Replay Filter REAL IDEAL IDEAL Env Env REAL
11 SymmetricKey Encryption RECALL Alternately (slightly weaker form): Adv can send its own messages SIMCCA Security Send Recv Key/Enc Key/Dec SIMCCA secure if: s.t. Replay Filter REAL IDEAL IDEAL Env Env REAL
12 SymmetricKey Encryption RECALL INDCCA Security Experiment picks b {0,1} and K KeyGen Adv gets (guarded) access to Dec K oracle For as long as Adversary wants Key/Enc Enc(m b,k) INDCCA + ~correctness equivalent to SIMCCA Key/Dec Adv sends two messages m 0, m 1 to the experiment Expt returns Enc(m b,k) to the adversary m b m 0,m 1 No challenge ciphertext answered Adversary returns a guess b Experiments outputs 1 iff b =b INDCCA secure if for all feasible adversaries Pr[b =b] 1/2 b b b {0,1} b =b? Yes/No
13 SymmetricKey Encryption RECALL INDCCA Security Experiment picks b {0,1} and K KeyGen Adv gets (guarded) access to Dec K oracle For as long as Adversary wants Key/Enc Weaker Enc(m b,k) INDCCA + ~correctness equivalent to SIMCCA Key/Dec Adv sends two messages m 0, m 1 to the experiment Expt returns Enc(m b,k) to the adversary m b m 0,m 1 No challenge ciphertext answered Adversary returns a guess b Experiments outputs 1 iff b =b INDCCA secure if for all feasible adversaries Pr[b =b] 1/2 b b b {0,1} b =b? Yes/No
14 CCA Security
15 CCA Security How to obtain CCA security?
16 CCA Security How to obtain CCA security? Use a CPAsecure encryption scheme, but make sure Bob accepts and decrypts only ciphertexts produced by Alice
17 CCA Security How to obtain CCA security? Use a CPAsecure encryption scheme, but make sure Bob accepts and decrypts only ciphertexts produced by Alice i.e., Eve can t create new ciphertexts that will be accepted by Bob
18 CCA Security How to obtain CCA security? Use a CPAsecure encryption scheme, but make sure Bob accepts and decrypts only ciphertexts produced by Alice i.e., Eve can t create new ciphertexts that will be accepted by Bob Achieves the stronger guarantee: in IDEAL, Eve can t send its own messages to Bob
19 CCA Security How to obtain CCA security? Use a CPAsecure encryption scheme, but make sure Bob accepts and decrypts only ciphertexts produced by Alice i.e., Eve can t create new ciphertexts that will be accepted by Bob Achieves the stronger guarantee: in IDEAL, Eve can t send its own messages to Bob CCA secure SKE reduces to the problem of CPA secure SKE and (shared key) message authentication
20 CCA Security How to obtain CCA security? Use a CPAsecure encryption scheme, but make sure Bob accepts and decrypts only ciphertexts produced by Alice i.e., Eve can t create new ciphertexts that will be accepted by Bob Achieves the stronger guarantee: in IDEAL, Eve can t send its own messages to Bob CCA secure SKE reduces to the problem of CPA secure SKE and (shared key) message authentication MAC: Message Authentication Code
21 Message Authentication Codes
22 Message Authentication Codes A single short key shared by Alice and Bob
23 Message Authentication Codes A single short key shared by Alice and Bob Can sign any (polynomial) number of messages
24 Message Authentication Codes A single short key shared by Alice and Bob Can sign any (polynomial) number of messages A triple (KeyGen, MAC, Verify) MAC K Ver K
25 Message Authentication Codes A single short key shared by Alice and Bob Can sign any (polynomial) number of messages A triple (KeyGen, MAC, Verify) MAC K Ver K Correctness: For all K from KeyGen, and all messages M, Verify K (M,MAC K (M))=1
26 Message Authentication Codes A single short key shared by Alice and Bob Can sign any (polynomial) number of messages A triple (KeyGen, MAC, Verify) Correctness: For all K from KeyGen, and all messages M, Verify K (M,MAC K (M))=1 Security: probability that an adversary can produce (M,s) s.t. Verify K (M,s)=1 is negligible unless Alice produced an output s=mac K (M) MAC K s i = MAC K (M i ) M i (M,s) Ver K Ver K (M,s) Advantage = Pr[ Ver K (M,s)=1 and (M,s) {(M i,s i )} ]
27 CCA Secure SKE
28 CCA Secure SKE CCAEnc K1,K2 (m) = ( c:= CPAEnc K1 (m), t:= MAC K2 (c) )
29 CCA Secure SKE CCAEnc K1,K2 (m) = ( c:= CPAEnc K1 (m), t:= MAC K2 (c) ) CPA secure encryption: Blockcipher/CTR mode construction
30 CCA Secure SKE CCAEnc K1,K2 (m) = ( c:= CPAEnc K1 (m), t:= MAC K2 (c) ) CPA secure encryption: Blockcipher/CTR mode construction MAC: from a PRF or BlockCipher (coming up)
31 CCA Secure SKE CCAEnc K1,K2 (m) = ( c:= CPAEnc K1 (m), t:= MAC K2 (c) ) CPA secure encryption: Blockcipher/CTR mode construction MAC: from a PRF or BlockCipher (coming up) SKE in practice can just use BlockCiphers (coming up)
32 CCA Secure SKE CCAEnc K1,K2 (m) = ( c:= CPAEnc K1 (m), t:= MAC K2 (c) ) CPA secure encryption: Blockcipher/CTR mode construction MAC: from a PRF or BlockCipher (coming up) SKE in practice can just use BlockCiphers (coming up) In principle, constructions (less efficient) possible based on any OneWay Permutation or even any OneWay Function
33 Making a MAC
34 Onetime MAC MAC Ver
35 Onetime MAC To sign a single n bit message MAC Ver
36 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme MAC Ver
37 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC Ver r r r r r r
38 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC 010 Ver r r r r r r
39 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme 010 Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC r 1 0 r 2 1 r 3 0 Ver Signature for m 1...m n be (r i mi) i=1..n r r r r r r
40 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme 010 Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC r 1 0 r 2 1 r 3 0 Ver Signature for m 1...m n be (r i mi) i=1..n Negligible probability that Eve can produce a signature on m m r r r r r r
41 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme 010 Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC r 1 0 r 2 1 r 3 0 Ver Signature for m 1...m n be (r i mi) i=1..n Negligible probability that Eve can produce a signature on m m r r r r r r Doesn t require any computational restrictions on adversary!
42 Onetime MAC To sign a single n bit message A simple (but inefficient) scheme 010 Shared secret key: 2n random strings (each kbit long) (r i 0,r i 1) i=1..n MAC r 1 0 r 2 1 r 3 0 Ver Signature for m 1...m n be (r i mi) i=1..n Negligible probability that Eve can produce a signature on m m r r r r r r Doesn t require any computational restrictions on adversary! More efficient onetime MACs exist (later)
43 (Multimsg) MAC from PRF When Each Message is a Single Block
44 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC!
45 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF
46 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF M F K F K (M)
47 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF Ver K (M,S) := 1 iff S=F K (M) M F K F K (M)
48 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF Ver K (M,S) := 1 iff S=F K (M) Output length of F K should be big enough M F K F K (M)
49 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF Ver K (M,S) := 1 iff S=F K (M) Output length of F K should be big enough M F K F K (M) If an adversary forges MAC with probability MAC, then can break PRF with advantage O( MAC 2 m(k) ) (m(k) being the output length of the PRF) [How?]
50 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF Ver K (M,S) := 1 iff S=F K (M) Output length of F K should be big enough M F K F K (M) If an adversary forges MAC with probability MAC, then can break PRF with advantage O( MAC 2 m(k) ) (m(k) being the output length of the PRF) [How?] Advantage in breaking a PRF F: diff in prob a test has of outputting 1, when given F vs. truly random R
51 (Multimsg) MAC from PRF When Each Message is a Single Block PRF is a MAC! MAC K (M) := F K (M) where F is a PRF Ver K (M,S) := 1 iff S=F K (M) Output length of F K should be big enough M F K F K (M) If an adversary forges MAC with probability MAC, then can break PRF with advantage O( MAC 2 m(k) ) (m(k) being the output length of the PRF) [How?] If random function R used as MAC, then probability of forgery, MAC* = 2 m(k) Advantage in breaking a PRF F: diff in prob a test has of outputting 1, when given F vs. truly random R
52 MAC for MultipleBlock Messages
53 MAC for MultipleBlock Messages What if message is longer than one block?
54 MAC for MultipleBlock Messages What if message is longer than one block? MAC ing each block separately is not secure (unlike in the case of CPA secure encryption)
55 MAC for MultipleBlock Messages What if message is longer than one block? MAC ing each block separately is not secure (unlike in the case of CPA secure encryption) Eve can rearrange the blocks/drop some blocks
56 MAC for MultipleBlock Messages What if message is longer than one block? MAC ing each block separately is not secure (unlike in the case of CPA secure encryption) Eve can rearrange the blocks/drop some blocks Could use a PRF that takes longer inputs
57 MAC for MultipleBlock Messages What if message is longer than one block? MAC ing each block separately is not secure (unlike in the case of CPA secure encryption) Eve can rearrange the blocks/drop some blocks Could use a PRF that takes longer inputs Can we use a PRF with a fixed blocklength (i.e., a block cipher)?
58 MAC for MultipleBlock Messages
59 MAC for MultipleBlock Messages A simple solution: tie the blocks together
60 MAC for MultipleBlock Messages A simple solution: tie the blocks together Add to each block a random string r (same r for all blocks), total number of blocks, and a sequence number
61 MAC for MultipleBlock Messages A simple solution: tie the blocks together Add to each block a random string r (same r for all blocks), total number of blocks, and a sequence number B i = (r, t, i, M i )
62 MAC for MultipleBlock Messages A simple solution: tie the blocks together Add to each block a random string r (same r for all blocks), total number of blocks, and a sequence number B i = (r, t, i, M i ) MAC(M) = (r, (MAC(B i )) i=1..t )
63 MAC for MultipleBlock Messages A simple solution: tie the blocks together Add to each block a random string r (same r for all blocks), total number of blocks, and a sequence number B i = (r, t, i, M i ) MAC(M) = (r, (MAC(B i )) i=1..t ) r prevents mixing blocks from two messages, t prevents dropping blocks and i prevents rearranging
64 MAC for MultipleBlock Messages A simple solution: tie the blocks together Add to each block a random string r (same r for all blocks), total number of blocks, and a sequence number B i = (r, t, i, M i ) MAC(M) = (r, (MAC(B i )) i=1..t ) r prevents mixing blocks from two messages, t prevents dropping blocks and i prevents rearranging Inefficient! Tag length increases with message length
65 CBCMAC
66 CBCMAC PRF domain extension: Chaining the blocks
67 CBCMAC PRF domain extension: Chaining the blocks m 1 m 2 m t... F K F K F K T
68 CBCMAC PRF domain extension: Chaining the blocks cf. CBC mode for encryption (which is not a MAC!) m 1 m 2 m t... F K F K F K T
69 CBCMAC PRF domain extension: Chaining the blocks cf. CBC mode for encryption (which is not a MAC!) tblock messages, a single block tag m 1 m 2 m t... F K F K F K T
70 CBCMAC PRF domain extension: Chaining the blocks cf. CBC mode for encryption (which is not a MAC!) tblock messages, a single block tag Can be shown to be secure m 1 m 2 m t... F K F K F K T
71 CBCMAC PRF domain extension: Chaining the blocks cf. CBC mode for encryption (which is not a MAC!) tblock messages, a single block tag Can be shown to be secure m 1 m 2 m t... F K F K F K T If restricted to tblock messages (i.e., same length)
72 CBCMAC PRF domain extension: Chaining the blocks cf. CBC mode for encryption (which is not a MAC!) tblock messages, a single block tag Can be shown to be secure m 1 m 2 m t... F K F K F K T If restricted to tblock messages (i.e., same length) Else attacks possible (by extending a previously signed message)
73 Patching CBCMAC
74 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is):
75 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks
76 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks
77 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks Important that first block is used: if last block, message extension attacks still possible
78 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks Important that first block is used: if last block, message extension attacks still possible EMAC: Output not the last tag T, but F K (T), where K is an independent key (after padding the message to an integral number of blocks). No need to know message length a priori.
79 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks Important that first block is used: if last block, message extension attacks still possible EMAC: Output not the last tag T, but F K (T), where K is an independent key (after padding the message to an integral number of blocks). No need to know message length a priori. CMAC: XOR last block with another key (derived from the original key using the blockcipher). Avoids padding when message is integral number of blocks.
80 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks Important that first block is used: if last block, message extension attacks still possible EMAC: Output not the last tag T, but F K (T), where K is an independent key (after padding the message to an integral number of blocks). No need to know message length a priori. CMAC: XOR last block with another key (derived from the original key using the blockcipher). Avoids padding when message is integral number of blocks. NIST Recommendation. 2005
81 Patching CBCMAC Patching CBC MAC to handle message of any (polynomial) length but still producing a single block tag (secure if blockcipher is): Derive K as F K (t), where t is the number of blocks Use first block to specify number of blocks Important that first block is used: if last block, message extension attacks still possible EMAC: Output not the last tag T, but F K (T), where K is an independent key (after padding the message to an integral number of blocks). No need to know message length a priori. CMAC: XOR last block with another key (derived from the original key using the blockcipher). Avoids padding when message is integral number of blocks. NIST Recommendation Later: Hashbased HMAC used in TLS and IPSec IETF Standard. 1997
82 SKE in Practice
83 Stream Ciphers
84 Stream Ciphers Used for onetime encryption
85 Stream Ciphers Used for onetime encryption RC4, estream portfolio,...
86 Stream Ciphers Used for onetime encryption RC4, estream portfolio,... In practice, stream ciphers take a key and an IV (for initialization vector) as inputs
87 Stream Ciphers Used for onetime encryption RC4, estream portfolio,... Also used to denote the random nonce chosen for encryption using a blockcipher In practice, stream ciphers take a key and an IV (for initialization vector) as inputs
88 Stream Ciphers Used for onetime encryption RC4, estream portfolio,... Also used to denote the random nonce chosen for encryption using a blockcipher In practice, stream ciphers take a key and an IV (for initialization vector) as inputs Heuristic goal: behave somewhat like a PRF (instead of a PRG) so that it can be used for multimessage encryption
89 Stream Ciphers Used for onetime encryption RC4, estream portfolio,... Also used to denote the random nonce chosen for encryption using a blockcipher In practice, stream ciphers take a key and an IV (for initialization vector) as inputs Heuristic goal: behave somewhat like a PRF (instead of a PRG) so that it can be used for multimessage encryption But often breaks if used this way
90 Stream Ciphers Used for onetime encryption RC4, estream portfolio,... Also used to denote the random nonce chosen for encryption using a blockcipher In practice, stream ciphers take a key and an IV (for initialization vector) as inputs Heuristic goal: behave somewhat like a PRF (instead of a PRG) so that it can be used for multimessage encryption But often breaks if used this way NIST Standard: For multimessage encryption, use a blockcipher in CTR mode
91 Block Ciphers
92 Block Ciphers DES, 3DES, Blowfish, AES,...
93 Block Ciphers DES, 3DES, Blowfish, AES,... Heuristic constructions
94 Block Ciphers DES, 3DES, Blowfish, AES,... Heuristic constructions Permutations that can be inverted with the key
95 Block Ciphers DES, 3DES, Blowfish, AES,... Heuristic constructions Permutations that can be inverted with the key Speed (hardware/software) is of the essence
96 Block Ciphers DES, 3DES, Blowfish, AES,... Heuristic constructions Permutations that can be inverted with the key Speed (hardware/software) is of the essence But should withstand known attacks
97 Block Ciphers DES, 3DES, Blowfish, AES,... Heuristic constructions Permutations that can be inverted with the key Speed (hardware/software) is of the essence But should withstand known attacks As a PRP (or at least, against key recovery)
98 Feistel Network
99 Feistel Network Building a permutation from a (block) function
100 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function
101 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) f 1
102 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) f 1
103 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) f 1
104 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) Given functions f 1,...,f t can build a tlayer Feistel network F f1...ft f 1
105 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) Given functions f 1,...,f t can build a tlayer Feistel network F f1...ft f1 f 2
106 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) Given functions f 1,...,f t can build a tlayer Feistel network F f1...ft Still a permutation from {0,1} 2m to {0,1} 2m f1 f 2
107 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) Given functions f 1,...,f t can build a tlayer Feistel network F f1...ft Still a permutation from {0,1} 2m to {0,1} 2m LubyRackoff: A 3layer Feistel network, in which 3 PRFs with independent seeds are the 3 round functions, is a PRP. A 4layer Feistel gives a strong PRP f1 f 2
108 Feistel Network Building a permutation from a (block) function Let f: {0,1} m {0,1} m be an arbitrary function F f : {0,1} 2m {0,1} 2m defined as F f (x,y) = ( y, x f(y) ) F f is a permutation (Why?) Can invert (How?) Given functions f 1,...,f t can build a tlayer Feistel network F f1...ft Still a permutation from {0,1} 2m to {0,1} 2m LubyRackoff: A 3layer Feistel network, in which 3 PRFs with independent seeds are the 3 round functions, is a PRP. A 4layer Feistel gives a strong PRP Fewer layers do not suffice! [Exercise] f1 f 2
109 DES Block Cipher
110 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX
111 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps)
112 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc
113 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse
114 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse Defined for fixed key/block lengths (56 bits and 64 bits); key is used to generate subkeys for round functions
115 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse Defined for fixed key/block lengths (56 bits and 64 bits); key is used to generate subkeys for round functions DES s key length too short
116 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse Defined for fixed key/block lengths (56 bits and 64 bits); key is used to generate subkeys for round functions DES s key length too short Can now mount brute force keyrecovery attacks (e.g. using $10K hardware, running for under a week, in 2006; now, in under a day)
117 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse Defined for fixed key/block lengths (56 bits and 64 bits); key is used to generate subkeys for round functions DES s key length too short Can now mount brute force keyrecovery attacks (e.g. using $10K hardware, running for under a week, in 2006; now, in under a day) DESX: extra keys to pad input and output
118 NIST Standard DES Block Cipher Data Encryption Standard (DES), TripleDES, DESX DES uses a 16layer Feistel network (and a few other steps) The round functions are not PRFs, but ad hoc Confuse and diffuse Defined for fixed key/block lengths (56 bits and 64 bits); key is used to generate subkeys for round functions DES s key length too short Can now mount brute force keyrecovery attacks (e.g. using $10K hardware, running for under a week, in 2006; now, in under a day) DESX: extra keys to pad input and output Triple DES: 3 successive applications of DES (or DES 1 ) with 3 keys
119 AES Block Cipher
120 NIST Standard AES Block Cipher Advanced Encryption Standard (AES)
121 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits)
122 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES)
123 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks
124 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks Has some algebraic structure
125 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks Has some algebraic structure Operations in a vector space over the field GF(2 8 )
126 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks Has some algebraic structure Operations in a vector space over the field GF(2 8 ) The algebraic structure may lead to attacks?
127 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks Has some algebraic structure Operations in a vector space over the field GF(2 8 ) The algebraic structure may lead to attacks? Some implementations may lead to sidechannel attacks (e.g. cachetiming attacks)
128 NIST Standard AES Block Cipher Advanced Encryption Standard (AES) AES128, AES192, AES256 (3 key sizes; block size = 128 bits) Very efficient in software implementations (unlike DES) Uses SubstituteandPermute instead of Feistel networks Has some algebraic structure Operations in a vector space over the field GF(2 8 ) The algebraic structure may lead to attacks? Some implementations may lead to sidechannel attacks (e.g. cachetiming attacks) No simple hardness assumption known to imply any sort of security for AES
129 By Jeff Moser (
130 Cryptanalysis
131 Cryptanalysis Attacking stream ciphers and block ciphers
132 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery
133 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery Brute force cryptanalysis, using specialized hardware
134 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery Brute force cryptanalysis, using specialized hardware e.g. Attack on DES in 1998
135 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery Brute force cryptanalysis, using specialized hardware e.g. Attack on DES in 1998 Several other analytical techniques to speed up attacks
136 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery Brute force cryptanalysis, using specialized hardware e.g. Attack on DES in 1998 Several other analytical techniques to speed up attacks Sometimes theoretical : on weakened ( reduced round ) constructions, showing improvement over bruteforce attack
137 Cryptanalysis Attacking stream ciphers and block ciphers Typically for key recovery Brute force cryptanalysis, using specialized hardware e.g. Attack on DES in 1998 Several other analytical techniques to speed up attacks Sometimes theoretical : on weakened ( reduced round ) constructions, showing improvement over bruteforce attack Meetinthemiddle, linear cryptanalysis, differential cryptanalysis, impossible differential cryptanalysis, boomerang attack, integral cryptanalysis, cube attack,...
138 Authenticated Encryption
139 Authenticated Encryption Doing encryption + authentication better
140 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC
141 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes
142 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes AE aims to do this more efficiently
143 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes AE aims to do this more efficiently Several constructions based on blockciphers (modes of operation) provably secure modeling blockcipher as PRP
144 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes AE aims to do this more efficiently Several constructions based on blockciphers (modes of operation) provably secure modeling blockcipher as PRP One pass: IAPM, OCB,... [patented]
145 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes AE aims to do this more efficiently Several constructions based on blockciphers (modes of operation) provably secure modeling blockcipher as PRP One pass: IAPM, OCB,... [patented] Two pass: CCM, GCM, SIV,... [included in NIST standards]
146 Authenticated Encryption Doing encryption + authentication better Generic composition: encrypt, then MAC Needs two keys and two passes AE aims to do this more efficiently Several constructions based on blockciphers (modes of operation) provably secure modeling blockcipher as PRP One pass: IAPM, OCB,... [patented] Two pass: CCM, GCM, SIV,... [included in NIST standards] AE with Associated Data: Allows unencrypted (but authenticated) parts of the plaintext, for headers etc.
147 SKE today
148 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers
149 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256
150 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC)
151 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC) Gives CCA security, and provides authentication
152 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC) Gives CCA security, and provides authentication Older components/modes still in use
153 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC) Gives CCA security, and provides authentication Older components/modes still in use Supported by many standards for legacy purposes
154 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC) Gives CCA security, and provides authentication Older components/modes still in use Supported by many standards for legacy purposes In many applications (sometimes with modifications)
155 SKE today SKE in IPsec, TLS etc. mainly based on AES blockciphers AES128, AES192, AES256 Recommended: AES Countermode + CMAC (or HMAC) Gives CCA security, and provides authentication Older components/modes still in use Supported by many standards for legacy purposes In many applications (sometimes with modifications) e.g. RC4 in BitTorrent, Skype, PDF
Symmetric Crypto MAC. PierreAlain Fouque
Symmetric Crypto MAC PierreAlain Fouque Birthday Paradox In a set of D elements, by picking at random D elements, we have with high probability a collision two elements are equal D=365, about 23 people
More informationlundi 1 octobre 2012 In a set of N elements, by picking at random N elements, we have with high probability a collision two elements are equal
Symmetric Crypto PierreAlain Fouque Birthday Paradox In a set of N elements, by picking at random N elements, we have with high probability a collision two elements are equal N=365, about 23 people are
More informationAuthenticated encryption
Authenticated encryption Dr. Enigma Department of Electrical Engineering & Computer Science University of Central Florida wocjan@eecs.ucf.edu October 16th, 2013 Active attacks on CPAsecure encryption
More informationTalk announcement please consider attending!
Talk announcement please consider attending! Where: Maurer School of Law, Room 335 When: Thursday, Feb 5, 12PM 1:30PM Speaker: Rafael Pass, Associate Professor, Cornell University, Topic: Reasoning Cryptographically
More informationLecture 9  Message Authentication Codes
Lecture 9  Message Authentication Codes Boaz Barak March 1, 2010 Reading: BonehShoup chapter 6, Sections 9.1 9.3. Data integrity Until now we ve only been interested in protecting secrecy of data. However,
More informationLecture 13: Message Authentication Codes
Lecture 13: Message Authentication Codes Last modified 2015/02/02 In CCA security, the distinguisher can ask the library to decrypt arbitrary ciphertexts of its choosing. Now in addition to the ciphertexts
More information1 Construction of CCAsecure encryption
CSCI 5440: Cryptography Lecture 5 The Chinese University of Hong Kong 10 October 2012 1 Construction of secure encryption We now show how the MAC can be applied to obtain a secure encryption scheme.
More informationTable of Contents. Bibliografische Informationen http://dnb.info/996514864. digitalisiert durch
1 Introduction to Cryptography and Data Security 1 1.1 Overview of Cryptology (and This Book) 2 1.2 Symmetric Cryptography 4 1.2.1 Basics 4 1.2.2 Simple Symmetric Encryption: The Substitution Cipher...
More informationAuthentication and Encryption: How to order them? Motivation
Authentication and Encryption: How to order them? Debdeep Muhopadhyay IIT Kharagpur Motivation Wide spread use of internet requires establishment of a secure channel. Typical implementations operate in
More informationProvableSecurity Analysis of Authenticated Encryption in Kerberos
ProvableSecurity Analysis of Authenticated Encryption in Kerberos Alexandra Boldyreva Virendra Kumar Georgia Institute of Technology, School of Computer Science 266 Ferst Drive, Atlanta, GA 303320765
More informationOverview of Cryptographic Tools for Data Security. Murat Kantarcioglu
UT DALLAS Erik Jonsson School of Engineering & Computer Science Overview of Cryptographic Tools for Data Security Murat Kantarcioglu Pag. 1 Purdue University Cryptographic Primitives We will discuss the
More informationLecture 10: CPA Encryption, MACs, Hash Functions. 2 Recap of last lecture  PRGs for one time pads
CS 7880 Graduate Cryptography October 15, 2015 Lecture 10: CPA Encryption, MACs, Hash Functions Lecturer: Daniel Wichs Scribe: Matthew Dippel 1 Topic Covered Chosen plaintext attack model of security MACs
More information1 Message Authentication
Theoretical Foundations of Cryptography Lecture Georgia Tech, Spring 200 Message Authentication Message Authentication Instructor: Chris Peikert Scribe: Daniel Dadush We start with some simple questions
More informationMessage Authentication Code
Message Authentication Code Ali El Kaafarani Mathematical Institute Oxford University 1 of 44 Outline 1 CBCMAC 2 Authenticated Encryption 3 Padding Oracle Attacks 4 Information Theoretic MACs 2 of 44
More informationEXAM questions for the course TTM4135  Information Security May 2013. Part 1
EXAM questions for the course TTM4135  Information Security May 2013 Part 1 This part consists of 5 questions all from one common topic. The number of maximal points for every correctly answered question
More informationCSCE 465 Computer & Network Security
CSCE 465 Computer & Network Security Instructor: Dr. Guofei Gu http://courses.cse.tamu.edu/guofei/csce465/ Secret Key Cryptography (I) 1 Introductory Remarks Roadmap Feistel Cipher DES AES Introduction
More information6.857 Computer and Network Security Fall Term, 1997 Lecture 4 : 16 September 1997 Lecturer: Ron Rivest Scribe: Michelle Goldberg 1 Conditionally Secure Cryptography Conditionally (or computationally) secure
More informationNetwork Security. Modes of Operation. Steven M. Bellovin February 3, 2009 1
Modes of Operation Steven M. Bellovin February 3, 2009 1 Using Cryptography As we ve already seen, using cryptography properly is not easy Many pitfalls! Errors in use can lead to very easy attacks You
More informationCS155. Cryptography Overview
CS155 Cryptography Overview Cryptography Is n A tremendous tool n The basis for many security mechanisms Is not n The solution to all security problems n Reliable unless implemented properly n Reliable
More informationCryptography and Network Security
Cryptography and Network Security Spring 2012 http://users.abo.fi/ipetre/crypto/ Lecture 3: Block ciphers and DES Ion Petre Department of IT, Åbo Akademi University January 17, 2012 1 Data Encryption Standard
More informationMessage Authentication Codes. Lecture Outline
Message Authentication Codes Murat Kantarcioglu Based on Prof. Ninghui Li s Slides Message Authentication Code Lecture Outline 1 Limitation of Using Hash Functions for Authentication Require an authentic
More informationCryptographic hash functions and MACs Solved Exercises for Cryptographic Hash Functions and MACs
Cryptographic hash functions and MACs Solved Exercises for Cryptographic Hash Functions and MACs Enes Pasalic University of Primorska Koper, 2014 Contents 1 Preface 3 2 Problems 4 2 1 Preface This is a
More informationDesigning Hash functions. Reviewing... Message Authentication Codes. and message authentication codes. We have seen how to authenticate messages:
Designing Hash functions and message authentication codes Reviewing... We have seen how to authenticate messages: Using symmetric encryption, in an heuristic fashion Using publickey encryption in interactive
More informationThe Order of Encryption and Authentication for Protecting Communications (Or: How Secure is SSL?)
The Order of Encryption and Authentication for Protecting Communications (Or: How Secure is SSL?) Hugo Krawczyk Abstract. We study the question of how to generically compose symmetric encryption and authentication
More informationBlock encryption. CS4920: Lecture 7 Secret key cryptography. Determining the plaintext ciphertext mapping. CS4920Lecture 7 4/1/2015
CS4920: Lecture 7 Secret key cryptography Reading Chapter 3 (pp. 5975, 9293) Today s Outcomes Discuss block and key length issues related to secret key cryptography Define several terms related to secret
More informationCryptographic Hash Functions Message Authentication Digital Signatures
Cryptographic Hash Functions Message Authentication Digital Signatures Abstract We will discuss Cryptographic hash functions Message authentication codes HMAC and CBCMAC Digital signatures 2 Encryption/Decryption
More informationMessage Authentication Codes
2 MAC Message Authentication Codes : and Cryptography Sirindhorn International Institute of Technology Thammasat University Prepared by Steven Gordon on 28 October 2013 css322y13s2l08, Steve/Courses/2013/s2/css322/lectures/mac.tex,
More informationCryptography and Network Security Chapter 6
Cryptography and Network Security Chapter 6 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 6 Block Cipher Operation Many savages at the present day regard
More informationCS 758: Cryptography / Network Security
CS 758: Cryptography / Network Security offered in the Fall Semester, 2003, by Doug Stinson my office: DC 3122 my email address: dstinson@uwaterloo.ca my web page: http://cacr.math.uwaterloo.ca/~dstinson/index.html
More informationAuthenticated Encryption: Relations among Notions and Analysis of the Generic Composition Paradigm By Mihir Bellare and Chanathip Namprempre
Authenticated Encryption: Relations among Notions and Analysis of the Generic Composition Paradigm By Mihir Bellare and Chanathip Namprempre Some slides were also taken from Chanathip Namprempre's defense
More informationLecture 4 Data Encryption Standard (DES)
Lecture 4 Data Encryption Standard (DES) 1 Block Ciphers Map nbit plaintext blocks to nbit ciphertext blocks (n = block length). For nbit plaintext and ciphertext blocks and a fixed key, the encryption
More informationGCMSIV: Full Nonce MisuseResistant Authenticated Encryption at Under One Cycle per Byte. Yehuda Lindell BarIlan University
GCMSIV: Full Nonce MisuseResistant Authenticated Encryption at Under One Cycle per Byte Shay Gueron Haifa Univ. and Intel Yehuda Lindell BarIlan University Appeared at ACM CCS 2015 How to Encrypt with
More informationOn the Security of CTR + CBCMAC
On the Security of CTR + CBCMAC NIST Modes of Operation Additional CCM Documentation Jakob Jonsson * jakob jonsson@yahoo.se Abstract. We analyze the security of the CTR + CBCMAC (CCM) encryption mode.
More informationSAMPLE EXAM QUESTIONS MODULE EE5552 NETWORK SECURITY AND ENCRYPTION ECE, SCHOOL OF ENGINEERING AND DESIGN BRUNEL UNIVERSITY UXBRIDGE MIDDLESEX, UK
SAMPLE EXAM QUESTIONS MODULE EE5552 NETWORK SECURITY AND ENCRYPTION September 2010 (reviewed September 2014) ECE, SCHOOL OF ENGINEERING AND DESIGN BRUNEL UNIVERSITY UXBRIDGE MIDDLESEX, UK NETWORK SECURITY
More informationCryptography and Network Security, PART IV: Reviews, Patches, and11.2012 Theory 1 / 53
Cryptography and Network Security, PART IV: Reviews, Patches, and Theory Timo Karvi 11.2012 Cryptography and Network Security, PART IV: Reviews, Patches, and11.2012 Theory 1 / 53 Key Lengths I The old
More informationModes of Operation of Block Ciphers
Chapter 3 Modes of Operation of Block Ciphers A bitblock encryption function f: F n 2 Fn 2 is primarily defined on blocks of fixed length n To encrypt longer (or shorter) bit sequences the sender must
More informationCryptography and Network Security Chapter 3
Cryptography and Network Security Chapter 3 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 3 Block Ciphers and the Data Encryption Standard All the afternoon
More informationCIS433/533  Computer and Network Security Cryptography
CIS433/533  Computer and Network Security Cryptography Professor Kevin Butler Winter 2011 Computer and Information Science A historical moment Mary Queen of Scots is being held by Queen Elizabeth and
More informationNetwork Security. Chapter 3 Symmetric Cryptography. Symmetric Encryption. Modes of Encryption. Symmetric Block Ciphers  Modes of Encryption ECB (1)
Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle Network Security Chapter 3 Symmetric Cryptography General Description Modes of ion Data ion Standard (DES)
More informationOverview of Symmetric Encryption
CS 361S Overview of Symmetric Encryption Vitaly Shmatikov Reading Assignment Read Kaufman 2.14 and 4.2 slide 2 Basic Problem   ? Given: both parties already know the same secret Goal: send
More informationLecture 5  Cryptography
CSE497b Introduction to Computer and Network Security  Spring 2007  Professors Jaeger Lecture 5  Cryptography CSE497b  Spring 2007 Introduction Computer and Network Security Professor Jaeger www.cse.psu.edu/~tjaeger/cse497bs07/
More informationMessage authentication
Message authentication  Hash based MAC unctions  MAC unctions based on bloc ciphers  Authenticated encryption (c) Levente Buttyán (buttyan@crysys.hu) Secret preix method MAC (x) = H( x) insecure!
More informationMessage Authentication Codes 133
Message Authentication Codes 133 CLAIM 4.8 Pr[Macforge A,Π (n) = 1 NewBlock] is negligible. We construct a probabilistic polynomialtime adversary A who attacks the fixedlength MAC Π and succeeds in
More informationError oracle attacks and CBC encryption. Chris Mitchell ISG, RHUL http://www.isg.rhul.ac.uk/~cjm
Error oracle attacks and CBC encryption Chris Mitchell ISG, RHUL http://www.isg.rhul.ac.uk/~cjm Agenda 1. Introduction 2. CBC mode 3. Error oracles 4. Example 1 5. Example 2 6. Example 3 7. Stream ciphers
More informationCryptography Overview
Cryptography Overview Cryptography Is n A tremendous tool n The basis for many security mechanisms Is not n The solution to all security problems n Reliable unless implemented properly n Reliable unless
More informationCryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur
Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Lecture No. # 11 Block Cipher Standards (DES) (Refer Slide
More informationCryptography & Network Security
Cryptography & Network Security Lecture 1: Introduction & Overview 2002. 3. 27 chlim@sejong.ac.kr Common Terms(1) Cryptography: The study of mathematical techniques related to aspects of information security
More informationChapter 8. Network Security
Chapter 8 Network Security Cryptography Introduction to Cryptography Substitution Ciphers Transposition Ciphers OneTime Pads Two Fundamental Cryptographic Principles Need for Security Some people who
More informationMessage Authentication
Message Authentication message authentication is concerned with: protecting the integrity of a message validating identity of originator nonrepudiation of origin (dispute resolution) will consider the
More information1 Signatures vs. MACs
CS 120/ E177: Introduction to Cryptography Salil Vadhan and Alon Rosen Nov. 22, 2006 Lecture Notes 17: Digital Signatures Recommended Reading. KatzLindell 10 1 Signatures vs. MACs Digital signatures
More informationCRYPTOGRAPHY IN NETWORK SECURITY
ELE548 Research Essays CRYPTOGRAPHY IN NETWORK SECURITY AUTHOR: SHENGLI LI INSTRUCTOR: DR. JIENCHUNG LO Date: March 5, 1999 Computer network brings lots of great benefits and convenience to us. We can
More informationCryptography and Network Security Chapter 12
Cryptography and Network Security Chapter 12 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 12 Message Authentication Codes At cats' green on the Sunday he
More informationCSC474/574  Information Systems Security: Homework1 Solutions Sketch
CSC474/574  Information Systems Security: Homework1 Solutions Sketch February 20, 2005 1. Consider slide 12 in the handout for topic 2.2. Prove that the decryption process of a oneround Feistel cipher
More informationAuthentication requirement Authentication function MAC Hash function Security of
UNIT 3 AUTHENTICATION Authentication requirement Authentication function MAC Hash function Security of hash function and MAC SHA HMAC CMAC Digital signature and authentication protocols DSS Slides Courtesy
More informationReconsidering Generic Composition
Reconsidering Generic Composition Chanathip Namprempre Thammasat University, Thailand Phillip Rogaway University of California, Davis, USA Tom Shrimpton Portland State University, USA 1/24 What is the
More informationCryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur
Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Module No. #01 Lecture No. #10 Symmetric Key Ciphers (Refer
More informationThe Data Encryption Standard (DES)
The Data Encryption Standard (DES) As mentioned earlier there are two main types of cryptography in use today  symmetric or secret key cryptography and asymmetric or public key cryptography. Symmetric
More informationDr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2010
CS 494/594 Computer and Network Security Dr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2010 1 Introduction to Cryptography What is cryptography?
More informationSPC5CRYPLIB. SPC5 Software Cryptography Library. Description. Features. SHA512 Random engine based on DRBGAES128
SPC5 Software Cryptography Library Data brief SHA512 Random engine based on DRBGAES128 RSA signature functions with PKCS#1v1.5 ECC (Elliptic Curve Cryptography): Key generation Scalar multiplication
More informationChapter 10. Network Security
Chapter 10 Network Security 10.1. Chapter 10: Outline 10.1 INTRODUCTION 10.2 CONFIDENTIALITY 10.3 OTHER ASPECTS OF SECURITY 10.4 INTERNET SECURITY 10.5 FIREWALLS 10.2 Chapter 10: Objective We introduce
More informationDeveloping and Investigation of a New Technique Combining Message Authentication and Encryption
Developing and Investigation of a New Technique Combining Message Authentication and Encryption Eyas ElQawasmeh and Saleem Masadeh Computer Science Dept. Jordan University for Science and Technology P.O.
More informationChapter 6 CDMA/802.11i
Chapter 6 CDMA/802.11i IC322 Fall 2014 Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross AddisonWesley March 2012 Some material copyright 19962012 J.F Kurose and K.W. Ross,
More informationDigital Signatures. Prof. Zeph Grunschlag
Digital Signatures Prof. Zeph Grunschlag (Public Key) Digital Signatures PROBLEM: Alice would like to prove to Bob, Carla, David,... that has really sent them a claimed message. E GOAL: Alice signs each
More informationChair for Network Architectures and Services Department of Informatics TU München Prof. Carle. Network Security. Chapter 13
Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle Network Security Chapter 13 Some More Secure Channel Issues Outline In the course we have yet only seen catastrophic
More informationCiphertext verification security of symmetric encryption schemes
www.scichina.com info.scichina.com www.springerlink.com Ciphertext verification security of symmetric encryption schemes HU ZhenYu 1, SUN FuChun 1 & JIANG JianChun 2 1 National Laboratory of Information
More informationClient Server Registration Protocol
Client Server Registration Protocol The ClientServer protocol involves these following steps: 1. Login 2. Discovery phase User (Alice or Bob) has K s Server (S) has hash[pw A ].The passwords hashes are
More informationSYMMETRIC ENCRYPTION. Mihir Bellare UCSD 1
SYMMETRIC ENCRYPTION Mihir Bellare UCSD 1 Syntax A symmetric encryption scheme SE = (K,E,D) consists of three algorithms: K and E may be randomized, but D must be deterministic. Mihir Bellare UCSD 2 Correct
More informationEXAM questions for the course TTM4135  Information Security June 2010. Part 1
EXAM questions for the course TTM4135  Information Security June 2010 Part 1 This part consists of 6 questions all from one common topic. The number of maximal points for every correctly answered question
More informationSecurity. Contents. S72.3240 Wireless Personal, Local, Metropolitan, and Wide Area Networks 1
Contents Security requirements Public key cryptography Key agreement/transport schemes Maninthemiddle attack vulnerability Encryption. digital signature, hash, certification Complete security solutions
More informationIT Networks & Security CERT Luncheon Series: Cryptography
IT Networks & Security CERT Luncheon Series: Cryptography Presented by Addam Schroll, IT Security & Privacy Analyst 1 Outline History Terms & Definitions Symmetric and Asymmetric Algorithms Hashing PKI
More informationLeakageResilient Authentication and Encryption from Symmetric Cryptographic Primitives
LeakageResilient Authentication and Encryption from Symmetric Cryptographic Primitives Olivier Pereira Université catholique de Louvain ICTEAM Crypto Group B1348, Belgium olivier.pereira@uclouvain.be
More informationNetwork Security. Omer Rana
Network Security Omer Rana CM0255 Material from: Cryptography Components Sender Receiver Plaintext Encryption Ciphertext Decryption Plaintext Encryption algorithm: Plaintext Ciphertext Cipher: encryption
More informationNetwork Security Technology Network Management
COMPUTER NETWORKS Network Security Technology Network Management Source Encryption E(K,P) Decryption D(K,C) Destination The author of these slides is Dr. Mark Pullen of George Mason University. Permission
More informationChapter 3. Network Domain Security
Communication System Security, Chapter 3, Draft, L.D. Chen and G. Gong, 2008 1 Chapter 3. Network Domain Security A network can be considered as the physical resource for a communication system. This chapter
More informationCryptoVerif Tutorial
CryptoVerif Tutorial Bruno Blanchet INRIA ParisRocquencourt bruno.blanchet@inria.fr November 2014 Bruno Blanchet (INRIA) CryptoVerif Tutorial November 2014 1 / 14 Exercise 1: preliminary definition SUFCMA
More informationOn the Security of the CCM Encryption Mode and of a Slight Variant
On the Security of the CCM Encryption Mode and of a Slight Variant PierreAlain Fouque 1 and Gwenaëlle Martinet 2 and Frédéric Valette 3 and Sébastien Zimmer 1 1 École normale supérieure, 45 rue d Ulm,
More informationLecture 15  Digital Signatures
Lecture 15  Digital Signatures Boaz Barak March 29, 2010 Reading KL Book Chapter 12. Review Trapdoor permutations  easy to compute, hard to invert, easy to invert with trapdoor. RSA and Rabin signatures.
More informationOutline. Computer Science 418. Digital Signatures: Observations. Digital Signatures: Definition. Definition 1 (Digital signature) Digital Signatures
Outline Computer Science 418 Digital Signatures Mike Jacobson Department of Computer Science University of Calgary Week 12 1 Digital Signatures 2 Signatures via Public Key Cryptosystems 3 Provable 4 Mike
More informationLecture 9  Network Security TDTS412006 (ht1)
Lecture 9  Network Security TDTS412006 (ht1) Prof. Dr. Christoph Schuba Linköpings University/IDA Schuba@IDA.LiU.SE Reading: Office hours: [Hal05] 10.110.2.3; 10.2.510.7.1; 10.8.1 910am on Oct. 4+5,
More informationNetwork Security. Abusayeed Saifullah. CS 5600 Computer Networks. These slides are adapted from Kurose and Ross 81
Network Security Abusayeed Saifullah CS 5600 Computer Networks These slides are adapted from Kurose and Ross 81 Goals v understand principles of network security: cryptography and its many uses beyond
More informationChapter 11 Security+ Guide to Network Security Fundamentals, Third Edition Basic Cryptography
Chapter 11 Security+ Guide to Network Security Fundamentals, Third Edition Basic Cryptography What Is Steganography? Steganography Process of hiding the existence of the data within another file Example:
More information1 Data Encryption Algorithm
Date: Monday, September 23, 2002 Prof.: Dr JeanYves Chouinard Design of Secure Computer Systems CSI4138/CEG4394 Notes on the Data Encryption Standard (DES) The Data Encryption Standard (DES) has been
More informationTinySec: A Link Layer Security Architecture for Wireless Sensor Networks
TinySec: A Link Layer Security Architecture for Wireless Sensor Networks Chris Karlof, Naveen Sastr, David Wagner Presented By: Tristan Brown Outline Motivation Cryptography Overview TinySec Design Implementation
More informationNetwork Security. Computer Networking Lecture 08. March 19, 2012. HKU SPACE Community College. HKU SPACE CC CN Lecture 08 1/23
Network Security Computer Networking Lecture 08 HKU SPACE Community College March 19, 2012 HKU SPACE CC CN Lecture 08 1/23 Outline Introduction Cryptography Algorithms Secret Key Algorithm Message Digest
More informationThe Advanced Encryption Standard: Four Years On
The Advanced Encryption Standard: Four Years On Matt Robshaw Reader in Information Security Information Security Group Royal Holloway University of London September 21, 2004 The State of the AES 1 The
More informationIdentitybased Encryption with PostChallenge Auxiliary Inputs for Secure Cloud Applications and Sensor Networks
Identitybased Encryption with PostChallenge Auxiliary Inputs for Secure Cloud Applications and Sensor Networks Tsz Hon Yuen  Huawei, Singapore Ye Zhang  Pennsylvania State University, USA Siu Ming
More information1 Domain Extension for MACs
CS 127/CSCI E127: Introduction to Cryptography Prof. Salil Vadhan Fall 2013 Reading. Lecture Notes 17: MAC Domain Extension & Digital Signatures KatzLindell Ÿ4.34.4 (2nd ed) and Ÿ12.012.3 (1st ed).
More informationAuthenticated Encryption: Relations among notions and analysis of the generic composition paradigm
An extended abstract of this paper appears in Tatsuaki Okamoto, editor, Advances in Cryptology ASIACRYPT 2000, Volume 1976 of Lecture Notes in Computer Science, pages 531 545, Kyoto, Japan, December 3
More informationNetwork Security CS 5490/6490 Fall 2015 Lecture Notes 8/26/2015
Network Security CS 5490/6490 Fall 2015 Lecture Notes 8/26/2015 Chapter 2: Introduction to Cryptography What is cryptography? It is a process/art of mangling information in such a way so as to make it
More informationSecurity and Authentication Primer
Security and Authentication Primer Manfred Jantscher and Peter H. Cole AutoID Labs White Paper WPHARDWARE025 Mr. Manfred Jantscher Visiting Master Student, School of Electrical and Electronics Engineering,
More informationHash Functions. Integrity checks
Hash Functions EJ Jung slide 1 Integrity checks Integrity vs. Confidentiality! Integrity: attacker cannot tamper with message! Encryption may not guarantee integrity! Intuition: attacker may able to modify
More informationSecurity Protocols/Standards
Security Protocols/Standards Security Protocols/Standards Security Protocols/Standards How do we actually communicate securely across a hostile network? Provide integrity, confidentiality, authenticity
More informationOutline. CSc 466/566. Computer Security. 8 : Cryptography Digital Signatures. Digital Signatures. Digital Signatures... Christian Collberg
Outline CSc 466/566 Computer Security 8 : Cryptography Digital Signatures Version: 2012/02/27 16:07:05 Department of Computer Science University of Arizona collberg@gmail.com Copyright c 2012 Christian
More informationCPS 590.5 Computer Security Lecture 9: Introduction to Network Security. Xiaowei Yang xwy@cs.duke.edu
CPS 590.5 Computer Security Lecture 9: Introduction to Network Security Xiaowei Yang xwy@cs.duke.edu Previous lectures Worm Fast worm design Today Network security Cryptography building blocks Existing
More informationInformation Security
SE 4472 / ECE 9064 Information Security Week 11: Transport Layer Security (TLS): Putting it all together Fall 2015 Prof. Aleksander Essex Security at the Transport Layer Where we started in this course:
More informationComputational Soundness of Symbolic Security and Implicit Complexity
Computational Soundness of Symbolic Security and Implicit Complexity Bruce Kapron Computer Science Department University of Victoria Victoria, British Columbia NII Shonan Meeting, November 37, 2013 Overview
More informationCS558. Network Security. Boston University, Computer Science. Midterm Spring 2014.
CS558. Network Security. Boston University, Computer Science. Midterm Spring 2014. Instructor: Sharon Goldberg March 25, 2014. 9:3010:50 AM. Onesided handwritten aid sheet allowed. No cell phone or calculators
More informationCryptography and Network Security
PARTA Questions 1. Name the aspects to be considered of information security. 2. What is meant by deciphering? 3. What are the two different uses of public key cryptography related to key distribution?
More informationThe Misuse of RC4 in Microsoft Word and Excel
The Misuse of RC4 in Microsoft Word and Excel Hongjun Wu Institute for Infocomm Research, Singapore hongjun@i2r.astar.edu.sg Abstract. In this report, we point out a serious security flaw in Microsoft
More informationMassachusetts Institute of Technology Handout 13 6.857: Network and Computer Security October 9, 2003 Professor Ronald L. Rivest.
Massachusetts Institute of Technology Handout 13 6.857: Network and Computer Security October 9, 2003 Professor Ronald L. Rivest Quiz 1 1. This quiz is intended to provide a fair measure of your understanding
More information