How To Find Out If Inraday Sock Price Reacions Are Worth It

Transcription

1 MOBILE BROKERAGE INFRASTRUCTURES CAPABILITIES AND SECURITY REQUIREMENTS Munermann, Jan; Rossnagel, Heiko; Rannenberg, Ka Universiy of Frankfur, Gräfsr. 78, Frankfur, Germany, [jan heiko Absrac This paper invesigaes he poenial of inegraed mobile financial informaion and ransacion services which can help privae invesors in making ime-criical invesmen decisions and porfolio ransacions in ime. The analysis of inraday sock price reacions following company announcemens provides evidence regarding he added value of such services if abnormal price movemens can be observed. As efficien capial markes reac very quickly o new informaion available, privae invesors require combined mobile noificaion and ransacion services. So far, exising conceps can no fulfill hese requiremens which resuls from inappropriae implemenaion of he securiy mechanisms in order o realize secure and rusworhy processing. Afer idenifying poenial weaknesses of curren soluions we inroduce an adequae sysem infrasrucure which can realize secure informaion and ransacion processing in ime by permiing a smar inegraion of noificaion and ransacion services. Keywords: Mobile Brokerage, Securiy Requiremens, Service Inegraion.

2 1 INTRODUCTION In recen years, financial services were expeced as one of he key commercial drivers for he mobile commerce marke (Durlacher Research 1999, Roland Berger 2000, Fros & Sullivan 2002). As we know oday, he marke developmen of mobile financial services including mobile banking and brokerage services has no lived up o hese expecaions. Reconsidering he implemenaions of mobile financial services available, so far we can find ha hey are mosly reproducions of heir (widely successful) web-based counerpars. This applies accordingly o he used securiy mechanisms. Consequenly, hey do no uilize heir special feaures deriving from he mobiliy and infrasrucural aspec. For example checking ou he balance of accouns or requesing sock prices migh be pasime bu does normally no provide added value for cusomers and using ransacion numbers for auhorizing ransacions while being on he way is inconvenien. As we can see from he success of equivalen online services, cusomers prefer doing heir daily (ime uncriical) ransacions using online services. E.g. a he end of 2003 nearly eighy percen of all checking accouns a privae banks in Germany were online accouns (Bundesverband Deuscher Banken 2004). In his paper we focus on his missing marke success of mobile financial services. Therefore, we analyze a promising applicaion domain (mobile brokerage noificaion and ransacion services) which can provide added value for cusomers and address he shorcomings of currenly used securiy mechanisms. Waching ou for an aracive and suiable applicaion area we find ha company announcemens can have significan shor erm price effecs on corresponding sock prices. If a privae invesor holds any socks of he company, he porfolio value can be affeced dramaically. As he resuling price effecs can be very promply and compleed wihin a shor ime frame, invesors should be noified and enabled o reac immediaely. In conras o mos of he exising mobile banking services our proposed applicaion domain can no be suppored by radiional online services. This domain focuses on a ime criical applicaion scenario which should be suppored in unexpeced siuaions. Therefore, we demonsrae he poenial added value of he proposed applicaion scenario in secion 2 by analyzing inraday sock price reacions following company announcemens. This is done by making an empirical analysis using voluminous hisorical inraday sock price series in order o prove he occurrence of relevan price effecs and o demonsrae he ime-criical speed of sock price adjusmens. Based on hese findings we examine he poenials resuling from an inegraion of mobile noificaion and ransacion services in secion 3. In order o suppor privae invesors o reac o an unexpeced marke even, i is necessary o inegrae mobile noificaion and ransacion services. As curren implemenaions seem o focus on securiy requiremens of ransacion services only and do no provide he posulaed service inegraion, we analyze applicaion and securiy requiremens of suiable mobile services in secion 4. Afer inroducing a ypical implemenaion concep including ypical shorcomings in secion 5 we inroduce an alernaive approach in secion 6, addressing he requiremens defined. Finally, in secion 7, we summarize our findings and give an oulook regarding furher research quesions and addiional implicaions concerning he proposed infrasrucure. 2 INTRADAY PRICE REACTIONS AND REACTION TIME In order o prove he applicaion domain of mobile brokerage noificaion and ransacion services we analyze inraday sock price reacions following company announcemens. If significan inraday price reacions can be proven, invesors should be noified promply.

3 Therefore, we formulae a research hypohesis regarding he informaion conen provided by company announcemens in order o prove he applicaion domain of mobile brokerage noificaion services. Hypohesis I: Company Announcemens cause significan inraday sock price reacions (which uncovers he poenial of added value provided by mobile brokerage noificaion services due o conemporary informaion supply). Furhermore, i is of umos imporance afer which ime frame he observed price reacions are compleed as invesors would have o reac wihin his period. Therefore, an analysis of his ime frame provides evidence regarding he window of opporuniy which opens for a limied period of ime only. If invesors mus reac quickly o ake he arising opporuniy, an inegraion of mobile noificaion and ransacion services is required. Consequenly, we formulae a second research hypohesis. Hypohesis II: The observed price effecs persis for a shor ime frame only (a few minues, up o one hour). This finding would prove he demand for an inegraion of mobile noificaion and ransacion services including promp ransacion auhorizaion. In order o prove boh research hypoheses we analyze he inraday sock price developmens following he company announcemens. 2.1 Price effec analysis The analysis covers price effecs following company announcemens pursuan o 15 of he German Securiies Trading Law. Our sample consiss of 172 company announcemens and covers he ime frame beween and The original daa sample consiss of 1694 company announcemens which had o be reduced by several filer rules. Firs, as we wan o observe inraday shor-run price effecs we discarded all announcemens which were no published during sock exchange rading hours. Concenraing on he German capial marke we eliminaed all announcemens of companies whose shares are lised a non-domesic sock exchanges only. To be able o analyze he price effec caused by he announcemen we discarded announcemens, if a company has published more han one announcemen per day (confounding evens) and if less han weny price fixings were available afer he announcemen dae. We begin wih he calculaion of discree reurns for company i a ime using inraday prices P. R = P + 1 P P (1) Inraday reurn of company i The inraday reurns are calculaed for all exising prices (and companies/announcemens) beween en days before and unil he announcemen day. These calculaed reurns represen he inraday sock price developmen of company i over a 10 day period. To isolae he price effec caused by he ad hoc disclosure, hese reurns have o be adjused by general marke developmens, i.e. he correced reurn series should only reflec price effecs caused by he ad hoc disclosure. In our work we calculae ne-of-marke-reurns o isolae he announcemen effec by applying a single index model (we use he CDAX index which conains all lised domesic companies represening he enire range of he German equiy marke). This is done for wo reasons. Firs, his model generaes beer resuls compared o he mean adjused reurns procedure and secondly i is no ouperformed by

4 he (more complex) OLS marke model (Klein and Rosenfeld 2002). These abnormal reurns (AR ) are worked ou by subracing he index (CDAX) reurns from he sock reurns R. AR R RCDAX, = (2) Abnormal reurns (marke-adjused) As we do no make ex ane announcemen classificaions, posiive and negaive announcemen effecs migh neuralize. Consequenly we use absolue values of he calculaed abnormal reurns (AAR ). These reurns can no be used for any saisical ess, because he sum of absolue values will always be significanly posiive wih high probabiliy. For ha reason we adjus hese absolue reurns by an average abnormal reurn which can be observed when no announcemen is published. These average absolue abnormal reurns (AAAR i ) cover he period beween en days before and wo days before he announcemen day. The day prior o he announcemen is excluded as hese prices migh be affeced by insider rading or anicipaion effecs. AAAR i T AR = = 1 T (3) Average absolue abnormal reurns The absolue abnormal reurns of he ime inervals o be analyzed are correced by hese averages. CAAR = ARi, AAAR i (4) Correced absolue abnormal reurns In comparison o Carer and Soo (1999) his CAAR can be inerpreed easily because we do no sandardize equaion 4. The CAAR is he par of he absolue abnormal reurns lying above an average which can be observed when no announcemen is published. For he saisical ess we calculae cumulaed correced absolue abnormal reurns CCAAR 1,2 for he price fixings following he announcemen. Cumulaed correced absolue abnormal reurns In order o prove our wo hypoheses we calculae CCAAR 1,2 for he sequenial ime frames (1,2) = (1,2), (3,5), (6,10), (11,15) and (16,20). These CCAAR 1,2 were calculaed for each ime frame and ad hoc disclosure and are used for our saisical ess. H H 2 CCAAR = CAAR 1, 2 = 1 ( ) 0 0 : E CCAAR 1, 2 = vs. ( ) 0 1 : E CCAAR 1, 2 > (5)

5 If we can rejec H 0 for a ime frame a a cerain significance level we can show significan price reacions wihin his ime frame. 2.2 Empirical resuls In order o prove our firs research hypohesis Mobile brokerage noificaion services provide added value if significan inraday sock price reacions following by company announcemens can be observed we perform -ess for each ime frame. Mean -value CCAAR 1, ** CCAAR 3, * CCAAR 6, CCAAR 11, CCAAR 16, ** indicaes significance on he 1% level; * on he 5% level Table 1. Inraday price reacion following by company announcemens Table 1 illusraes ha we can deec significan abnormal price reacions for he wo sequenial ime frames (1,2) and (3,5). Consequenly, we can corroborae hypohesis 1 as his price reacion asks for noificaion of he invesors. Furhermore, we can show ha he price reacion is compleed wihin he firs 5 price fixings following he publicaion. Depending on he rading volume of each sock hese five price fixings occur wihin differen ime frames (measured in minues). Figure 1 presens he disribuion regarding how many minues correspond wih he firs five price fixings. percen 40% 35% 36,6% 30% 25% 26,2% 20% 15% 15,1% 10% 5% 0% 7,6% 7,0% 2,9% 3,5% 1,2% >120 minues Figure 1. Time conversion of he firs five price fixings (n=172) Figure 1 illusraes ha nearly 80% of he firs five price fixings can be observed wihin he firs 30 minues following he publicaion (arihmeic mean of 23.2 minues). As his period of ime opens a shor window of opporuniy for invesors we can corroborae our second hypohesis An inegraion of mobile noificaion and ransacion services, including promp ransacion auhorizaion, is required if observed price effecs persis for a shor period of ime only.

6 Consequenly, an inelligen inegraion of he noificaion services wih he ransacion services is required or he invesor will no be able o benefi from he noificaion service. Furhermore, an invesmen decision has o be made when he invesor decides ha he announcemen requires porfolio ransacions. The analysis of inraday price reacions has shown ha here is a maximum of approximaely a few minues up o half an hour ime o reac afer which he price reacion is compleed. Consequenly, noificaion and ransacion services have o be inegraed services enabling invesors o reac promply as he available ime is required for he evaluaion of he invesmen decision o be made by he invesor. 3 POTENTIALS OF MOBILE BROKERAGE SERVICE INTEGRATION The poenials of mobile noificaion services are quie obvious considering he price effecs analyzed in secion 2. Using mobile noificaion services enables privae invesors o be informed permanenly abou relevan marke evens wihou observing he marke developmen coninuously. The addressed noificaion services can improve he level of informaion of privae invesors significanly and can pu hem on level playing field wih heir insiuional counerpars who observe all porfolio relevan marke news coninuously. Solely increasing he level of informaion by mobile noificaion services will no lead o promp invesmen success. Furhermore, invesors mus be empowered o perform necessary ransacions in ime or hey will no be able o ake advanage of he beer informaion siuaion. Consequenly, a sringen service inegraion of mobile noificaion and ransacion services is required which can no be fulfilled by exising conceps. This consrain arises from he fac ha securiy requiremens are addressed in a wrong way. These exising implemenaions are designed o achieve securiy bu no applicaion requiremens. Therefore we analyze general securiy and applicaion requiremens for he proposed noificaion and ransacion services in he nex secion o be able o derive an alernaive approach in order o bring hese securiy requiremens in line wih he applicaion requiremens (sringen inegraion of noificaion and ransacion services). 4 SECURITY AND APPLICATION REQUIREMENTS I is essenial for he invesor ha he whole process, saring wih he noificaion and leading o a possible ransacion, is as lile ime consuming and as much convenien as possible. This would enable he invesor o spend mos of he available ime for he decision making. Therefore, we formulae an applicaion requiremen. Requiremen I: The complee process of noificaion and ransacion services has o be as lile ime consuming and as much convenien as possible. Since invesors use a grea variey of differen mobile devices he service provider should have an ineres o design he service as compaible as possible o mos devices. Therefore, we formulae anoher applicaion requiremen. Requiremen II: The noificaion and ransacion services should be useable wih (almos) any mobile phone on he marke. Because of he shor ime span in which he invesor has o reac o he noificaion i is no possible o crosscheck he received informaion. Therefore, he noificaion service has o provide a way o ensure he inegriy and auheniciy of he noificaions. Oherwise, a poenial aacker could aler noificaion messages or creae false noificaion messages ha could lead o false decisions by he invesor. I is also imporan ha he noificaion does no ge los or delayed (availabiliy is he corresponding propery). Consequenly, we formulae a hird requiremen which should be fulfilled by

7 he noificaion service. Obviously, he noificaion service on is own canno guaranee fulfillmen of any of hese requiremens (e.g. when communicaions are inerruped or ampered wihin pars of he nework ouside of is conrol), bu i is imporan ha he user knows abou he sae of he message he ges. Requiremen III: The noificaion service has o provide means o ensure ha violaions of he inegriy or auheniciy of he noificaion message can be deeced by he receiver and o ensure ha he message reaches he invesor in ime. The linked ransacion services should also provide inegriy and accounabiliy of he process. In addiion, he communicaion beween he invesor and he online broker should be confidenial. Consequenly, we formulae a securiy requiremen for he ransacion service. Requiremen IV: The ransacion service should provide availabiliy, inegriy, accounabiliy and confidenialiy. Based on hese requiremens we formulae a research hypohesis regarding he securiy of he sysem infrasrucure. Hypohesis III: A soluion using a smar card (e.g. SIM) wih elecronic signaure funcionaliy will be a leas as secure as curren approaches Wih regard o service inegraion and service convenience we formulae a fourh research hypohesis. Hypohesis IV A smar card based approach can provide beer inegraion of mobile noificaion and ransacion services han curren approaches and is consequenly more adequae for he inroduced applicaion domain. In he following secion we will analyze curren approaches of mobile brokerage informaion and ransacion services wih regard o our requiremens. We will hen propose an infrasrucure wih he aim of corroboraing our hypoheses. 5 CURRENT APPROACHES Curren mobile brokerage services are usually implemened like radiional online brokerage services. Figure 2 illusraes such a sysem. Figure 2. Noificaion and ransacion sysem infrasrucure (curren) Afer he publicaion of he company announcemen he invesor receives a SMS noificaion wih he relevan informaion. The invesor will hen use he browser of his mobile device o connec o he ransacion server and eners he login daa (e.g. accoun number) and a personal idenificaion number (PIN). Now he invesor is able o perform ransacions bu has o confirm every single one wih a ransacion number (TAN).

8 This soluion does no fulfill Requiremen III. The SMS message conaining a relevan noificaion does no provide any proecion of inegriy or auheniciy. A poenial aacker will be able o pose as he news feed server sending false noificaions (GSMBox 2004). Since he noificaion is sen via SMS here is no guaraneed delivery (Schiller 2003). I is very inconvenien for he invesor o ener a ransacion number while being pressed for ime. Furhermore, he invesor has o carry a lis of TANs a all imes in order o be able o reac o incoming noificaions. This increases he risk of poenial hef or loss of he TAN lis. Therefore, we conclude ha despie being ime efficien as possible i does no fulfill Requiremen I. The German bank Posbank AG offers a service called mobile TAN (mtan) ha offers he invesor he possibiliy o reques a TAN online ha will be send o he invesor via SMS (Deusche Posbank AG 2004). Using his soluion he invesor is able o reac o incoming noificaion messages even if he TAN lis is a a differen locaion han he invesor. However, his soluion remains o be raher inconvenien since he invesor has o order he mtan online and afer receiving he corresponding SMS has o swich from he brokerage applicaion (mos likely a WAP browser) o he SMS clien. Then afer memorizing he mtan he invesor has o swich back o he brokerage applicaion, wasing valuable amouns of ime. Furhermore, his service adds a new securiy risk. The SMS conaining he mtan could be inerceped by a poenial aacker (because i is a plain ex message) and could be used o damage he invesor s porfolio saus or perform unwaned ransacions. However, he PIN/TAN soluion does fulfill Requiremen II, because no addiional sofware has o be used. Only a browser is needed and almos all curren mobile phones offer a leas a WAP-browser (Forreser Research 2003). Mos of he curren mobile brokerage providers use Wireless Transpor Layer Securiy (WTLS) and/or Secure Socke Layer (SSL) o encryp he daa ransfer beween cusomers and heir ransacion servers. These sandard encrypion proocols are commonly used and should provide he necessary amoun of daa confidenialiy. The PIN/TAN auhenicaion mehod ensures ha someone wih knowledge of he PIN and one of he TANs has ordered he ransacion made. The invesor is supposed o keep he PIN and all TANs confidenial. Therefore, he PIN and TANs should only be known by he invesor and he online broker. One could argue ha his is sufficien suppor of accounabiliy, bu he invesor has o rus he service provider. An aacker locaed inside he service provider wih access o he TANs could iniiae unwaned ransacions. There is also no way of ensuring he inegriy of he ordered ransacion. A rogue employee of he service provider could be able o aler he order made by he invesor. Oher problems can arise from he saeless ineracion paradigm of he web (Shegalov, Weikum, Barga and Lome 2002). Therefore, we conclude ha Requiremen IV is only parially me by curren mobile brokerage services. 6 PROPOSED INFRASTRUCTURE The infrasrucure we are going o propose is based on he assumpion ha he invesor is using a SIM card ha is capable of creaing elecronic signaures. The echnology for such SIM cards exiss bu has no gained much marke peneraion so far. The WiTness projec (European IST Projec 2004) sponsored by he European Union has developed such a SIM card ha is capable of creaing RSA signaures (Rives, Shamir and Adleman 1978) and also provides 3DES encrypion. Using such a SIM card he invesor can regiser his public key a he online broker and can obain a copy of he public key of he noificaion service provider. Having defined he necessary premises we can now propose he following infrasrucure ha is illusraed in Figure 3.

9 Figure 3. Noificaion and ransacion sysem infrasrucure (proposed) Our goal is o achieve as many of he applicaion and securiy requiremens defined in secion 4 as possible. Therefore, we propose an implemenaion using he SIM Applicaion Toolki (SIM AT) which also ensures compaibiliy o almos all mobile phones. Using SIM AT for supporing secure ransacion services has been proposed in he pas (Guhery and Cronin 2002) bu hese exising applicaion scenarios do no provide added value which can be achieved by focusing on promising applicaion domains (e.g. enabling invesors o reac o relevan evens in ime) and smar inegraion of mobile noificaion and ransacion services. When a company makes an announcemen during sock exchange rading hours he news feed server creaes a noificaion SMS and sends i o he SIM AT applicaion running on he mobile device of he invesor (European Telecommunicaions Sandards Insiue 1992). The SMS is elecronically signed wih he privae key of he service provider. Afer receiving he signed push noificaion he applicaion can check he inegriy and auheniciy of he noificaion by verifying he signaure. If he signaure is valid he invesor sars his brokerage clien. Afer making an invesmen decision he invesor connecs o he ransacion server and eners a PIN for user auhenicaion. If required, he invesor performs a sock order which is elecronically signed by he SIM AT applicaion using he digial signaure funcionaliy of he SIM AT applicaion (European Telecommunicaions Sandards Insiue 1999). In order o confirm his signaure he invesor has o ener a signaure PIN. The ransacion server verifies he signaure and complees he ransacion if he signaure is valid. As he used SMS service does no provide acknowledgemens for delivered messages, availabiliy can no be guaraneed. Therefore, addiional seps are necessary o make sure he invesor receives he needed informaion in ime. If he invesor does no reac a all o an incoming noificaion, he noificaion service resends he SMS 2 imes afer 10 and 20 minues. Noifying 3 imes provides a balance beween availabiliy and convenience. Anoher opion is o le he invesor configure he number and frequency of noificaion reransmissions. This soluion seems o be prey convenien and very ime efficien. Afer receiving he noificaion he invesor has direc access o he ransacion services afer enering he auhorizaion PIN. The ransacion process is compleed when he ransacion is confirmed wih a second signaure PIN. In conras o curren soluions his second PIN does no change, eliminaing he need o carry around a TAN lis. Therefore, we can sae ha Requiremen I has been me. Since mos curren mobile phones suppor SIM AT we can also conclude ha Requiremen II has been fulfilled. By checking he validiy of he elecronically signed noificaion message he SIM AT applicaion is able o check he auheniciy (only he service provider can make a valid signaure) and he inegriy of he noificaion

10 message auomaically. Moreover, noificaions are resen if he invesor shows no reacion. So we conclude ha Requiremen III has almos been fulfilled, as delivery can no be guaraneed. By signing he ransacion reques he invesor ensures he inegriy of his reques. I also guaranees ha only he invesor could have requesed his ransacion enabling accounabiliy. Confidenialiy can be provided by ciphering he daa ransfer beween he brokerage clien and he ransacion server using WTLS, SSL or 3DES. As he server is he general server for web ransacions, availabiliy is comparable o he non-mobile case. So we can sae ha Requiremen IV has been me. The proposed soluion has almos fulfilled he requiremens ha we defined in secion 4. Therefore, we can corroborae our hypoheses 3 and 4, because he proposed soluion provides beer securiy and beer inegraion of services han curren soluions. However, we mus admi ha he proposed soluion only works wih SIM-cards ha have no enered he marke ye. Consequenly one could argue ha mobile operaors will no have any ineres in providing more expensive SIM-cards equipped wih a crypographic coprocessor. On he oher hand he mobile operaor can expec an increase in raffic caused by noificaion and ransacion services ha possibly creaes enough new revenue o finance he addiional coss. Also he mobile operaor could sell signaure enabled SIM cards o early adopers a a higher price han normal SIMs and hereby pass on he addiional coss o he invesor. Furhermore, he mobile operaor conrols which applicaions can be run on he SIM. This enables him o charge he financial service provider for he mobile noificaion and ransacion services providing a new source of revenue. This of course raises he quesion why he financial service providers should le he mobile operaor paricipae on heir revenue sream. By providing mobile informaion services and by also enabling he invesor o make ransacions based on hese noificaions hey can expec an increase of financial ransacions. Therefore, hey can expec an increase of revenue ha can be shared wih oher paries. 7 CONCLUSION AND OUTLOOK In his paper we focused on applicaion domains of promising mobile brokerage services. Saring from he curren range of mobile brokerage services we criicized he missing added value from hese services ascribed o he fac ha mos of hese services are reproducions of web-based online banking services. In consequence, hese services do no uilize from heir mobile ubiquiy. Therefore, we proposed o suppor privae invesors by noifying hem abou relevan marke evens which migh have impac on heir porfolios. In order o demonsrae hese poenials we analyzed inraday sock price reacions which were caused by company announcemens. We found ou ha hese price reacions occur promply and are compleed wihin a ime frame of several minues. Our findings confirm he poenial of he respecive mobile noificaion services which provide relevan informaion supply ha can no be accomplished by radiional online services in ime. As invesors would wan o be able o reac by performing porfolio ransacions in ime, we recommended an inegraion of mobile noificaion and ransacion services. This inegraion can no be found in available conceps which seem o jus concenrae on securiy requiremens and neglec applicaion requiremens. Therefore, we formulaed securiy and applicaion requiremens which should be fulfilled by appropriae mobile brokerage services. Afer comparing hese requiremens wih ypical infrasrucures available oday, we found ou ha hey are me only parly. Therefore, we proposed an alernaive infrasrucure concep using mobile signaures suppored by he GSM Subscriber Ideniy Module (SIM) and he SIM Applicaion Toolki. We can show ha our concep mees mos of he posulaed applicaion and securiy requiremens and definiely more han exising infrasrucure conceps. Furhermore, we showed ha he proposed applicaion infrasrucure provides benefis for privae invesors, service providers and mobile nework operaors. This proposed infrasrucure could also be

11 used for legally binding elecronic signaures based on he EC-Direcive on a communiy framework for elecronic signaures (European Communiy 1999). As poined ou in Roßnagel (2004) i would be possible for financial service providers o ac as rus providers for advanced elecronic signaures issuing qualified cerificaes. This of course would require a cerificaion of he SIM card as well as he SIM AT applicaion agains common crieria. The proposed archiecure shows ha highly specialized and inegraed mobile brokerage services can add value o all paries involved and can be a componen for fuure services requiring binding elecronic signaures. Acknowledgemens The auhors hank Deusche Börse Group and DPA-AFX for providing he used daa sources. Furhermore, we would like o hank IS.Teledaa AG on whose server infrasrucure he even sudy has been performed. This work of Jan Munermann and Heiko Roßnagel is suppored by grans from T-Mobile Inernaional. We graefully acknowledge he suppor. References Bundesverband Deuscher Banken, Kunden der privaen Banken begeisere Online Banker, Carer, M. and B. Soo, "The relevance of Form 8-K Repors", Journal of Accouning Journal of Accouning Research 37 (1), 1999, pp Deusche Posbank AG, Posbank Direc Deails, Seie_ jsp, Durlacher Research Ld., Mobile Commerce Repor, London, European Communiy, Direcive 1999/93/EC of he European Parliamen and of he Council of 13 December 1999 on a Communiy Framework for Elecronic Signaures, Brussels, European IST Projec 'Wireless Trus for Mobile Business' (WiTness), SIM Applicaion Hosing - Deailed descripion of he concep, European Telecommunicaions Sandards Insiue, GSM Technical Realizaion of he Shor Message Service - Poin-o-Poin, Valbonne Cedex, France, European Telecommunicaions Sandards Insiue, GSM Securiy Mechanisms for he SIM applicaion oolk Sophia Anipolis Cedex, France, Forreser Research, European Mobile Forecas: 2003 To 2008, Amserdam, Fros & Sullivan, European Mobile Commerce Paymens, London, GSMBox Ld., GSMBOX - Homepage, uk.gsmbox.com, Guhery, S. B. and M. J. Cronin, Mobile Applicaion Developmen wih SMS and he SIM Toolk McGraw-Hill, New York, Klein, A. and J. Rosenfeld, "The influence of marke condiions on even-sudy residuals", Journal of Financial and Quaniaive Analysis 22 (3), 1987, pp Rives, R., L. Shamir and L. Adleman, "A Mehod for Obaining Digial Signaures and Public Key Cryposysems", Communicaions of he ACM 21 (2), 1978, pp Roland Berger, Dial M for Mobile - Key Success Facors in he Wireless World, New York, Roßnagel, H., "Mobile Qualified Signaures and Cerificaion on Demand", in: Proceedings of he 1s European PKI Workshop - Research and Applicaions, Springer LNCS, Berlin, Heidelberg, Schiller, J., Mobile Communicaions, Boson, MA, Addison-Wesley, Shegalov, G., Weikum G.; Barga, R. and D. Lome, "EOS: Exacly-Once E-Service Middleware", Hong Kong, China, 2002.