This report examines two scenarios in which Alice, a high net worth customer, is a victim of two cryptographic attacks. She suffers the first attack when banking at Super Secure Bank (SSB) where she uses a 3DES cryptography system to conduct her transactions and the second attack at Modern Security Trust (MST) where she uses the RSA cryptographic system. In both attacks, the attackers claim that Alice asked them to transfer a sum of $ 1,000,000 from her account to their own as a token of esteem and appreciation. Alice denies these claims and in both cases files a suit against the attacker, her bank and the government of the country to which the funds were transferred. This report examines the facts presented, offers a plausible explanation and suggests what the banks in question and Alice would have done to avoid such controversies from arising.
Taking into account the first scenario this report concludes that SSB switches to an AES cryptography system, boosts its internet defenses and institutes a policy that allows and encourages online bankers to operate their accounts on a dual control and approval basis. Taking into account the second scenario this report concludes that MST couples its RST cryptographic system with a padding scheme and implements a policy that allows and encourages online bankers to operate their accounts on a dual control and approval basis.
Introduction
In online banking, bank customers conduct their bank transactions online, that is, via the internet (wiseGEEK, 2011, p.1). The article “Why do organizations need information systems?” equates information to an organization with blood to a human being stressing on the importance of its proper management and security (Answers Corporation, 2011, p.2).
One way of enhancing information security in banks is cryptography, which is mainly a defence against internet-based attacks. It is the encoding of messages in such a way that its contents are hidden from any unauthorized principals (Coulouris et al, 2005, p.275). To unhide the contents of an encrypted message one has to know the cryptography key used and its encryption algorithm. Thus, as a measure to boost information security the cryptography key is kept a secret. In the face of attackers, cryptography boosts internet security by ensuring the secrecy and integrity of information through encryption and decryption of messages by authorized principals who themselves are not a security threat (Coulouris et al, 2005, p.276). Cryptography also boosts information security as it supports the authentication of communication between the principals involved in the process though cryptographic-based signatures (Coulouris et al, 2005, p.276).
An example of a cryptographic system is the Triple Data Encryption Standard (3DES), which is a variant and advancement of the Data Encryption Standard (Tropical Software, p.1). The large size of the 3DES facilitates the development of complex cryptography keys, which are arduous to crack and thus in effect discourage attacks. In this cryptography system, as the name suggests, when encrypting a message or a data block the data encryption standard (DES) is applied three times (Internet.com, 2011, p.3).
Another cryptography system is the advanced encryption standard (AES). According to Good, “AES is a Federal Information Processing Standard (FIPS) selected by the U.S. National Institute of Standards and Technology (NIST) for its combination of resistance to attack, ease of implementation, efficiency, and scalable design” (p.1). AES performs better when compared to 3DES. Another cryptography system is the Rivest, Shamir and Adleman (RSA) system. “RSA gets its security from the difficulty of factoring large numbers” (Ryan, 2008, p.16).
Discussion
Scenario One
What can be determined from the facts present
From the facts that emerge in the case between Alice and SSB it can be determined that the secrecy of the cryptography key used in Alice’s online financial transactions with SSB has been compromised. Most likely Bob, SSB’s bank manager has knowledge of this key. Again from the facts, it can be deduced that a tampering attack was effected targeting Alice’s online financial transactions with SSB.
A likely explanation for this is an internet based attack called a man-in-the-middle attack (Coulouris et al, 2005, p.269). The man-in-the-middle attack is a three-phased attack system (Coulouris et al, 2005, p.269). The first phase is the attacker establishing a secure channel through interception of the first message transmitted in that channel, which carries the encryption keys of the channel (Coulouris et al, 2005, p.269). The second phase in the attack is the attacker’s submission of compromised keys that enable him/her to decrypt any subsequent messages sent through the channel (Coulouris et al, 2005, p.269). The third phase in the attack is the actual tampering of messages: the message is decrypted, altered to the attacker’s satisfaction, reassembled to fit the correct key and then submitted (Coulouris et al, 2005, p.269). The most likely man-in-the-middle attacker in this case is Bob.
What could have been done to avoid the controversy from arising
To prevent the controversy from arising, both Alice and SSB should have ensured that online bank transactions are carried out in a dual control and approval environment thus enabling Alice to approve any transaction before it is initiated (Bank of San Antonio, 2011, p.10).
AES versus 3DES
The controversy would have arisen even if SSB was using an AES cryptographic system. This is because SSB online defences are weak therefore allowing attackers to steal communication channels and use them for their own malicious interests.
Scenario two
What can be determined from the facts present
Closely examining scenario two reveals that the case describes a classic chosen ciphertext attack and as such, Alice did not intend to give Frank a gift of $1,000,000. In this type of attack, the attacker works to obtain the decryption (or plaintext) of a given ciphertext, which is at the center of his or her malicious scheme. This attack is possible when you consider that RSA algorithms are such that “the product of two ciphertexts is equal to the encryption of the product of the respective plaintexts” (Ryan, 2008, p.40).
This being the case Frank is the attacker and Alice is yet again the victim. The ciphertext at the heart of Frank’s scheme is g, which claims he has been awarded $1,000,000 by Alice as a token of esteem and appreciation. From the calculation as described in the scenario it has been established that g = (ceA mod nA)dF mod nF where c is the plaintext send by Alice to Frank when enquiring about current interest rates on Certificates of Deposit issued by MST, {eA, nA} is Alice’s public key and {dF, nF} is Frank’s private key. Frank’s goal as the attacker was to obtain the decryption, m1, from Alice that results in the ciphertext, g. By taking into account the property stated above we assume that Frank additionally tricked Alice into decrypting an unsuspicious-looking ciphertext of the form c’ = cre (mod n) where r is a value appropriately chosen by Frank. By the property stated above, m1r (mod n) is the decryption of c’. Thus, Frank gets m1 as the quotient of the modular inverse of r modulo n and r. After getting m1, the next step in Frank’s scheme was switching Alice’s original message m with m1, therefore making it look like Alice was asking Frank to transfer money from her account to his account instead of enquiring about current interest rates on Certificates of Deposit issued by MST.
What could have been done to avoid the controversy from arising
One thing that SSB could have done to avoid this controversy from arising is adopting a padding scheme. According to Ryan Padding schemes are one of the ways of preventing RSA against attacks (2008, p.39). To prevent the controversy from arising, both Alice and SSB should have demanded to operate her online bank account on a dual control and approval basis in which she would have to approve any transaction before it is initiated (Bank of San Antonio, 2011, p.10)
Conclusion
SSB should switch from a 3DES cryptography system to an AES cryptography system as this guarantees more security. However, it is important for the bank to boost its defences against internet-based attacks and institute a policy that ensures that online bankers operate their accounts on a strict dual control and approval basis. To improve the performance of its RAS cryptographic system MST should adopt a RAS padding scheme as this will frustrate RAS-against attacks. In addition to this MST should institute a policy that allows online bankers to operate their accounts on a dual control and approval basis.
References
Answers Corporation. ( 2011). Why do organizations need information systems?. Web.
Bank of San Antonio. (2011). Online banking best practises. Web.
Coulouris, G. Dollimore, J. And Kindberg, T. ( 2005). Distributed systems concepts and design. (4th ed.). Pearson Education Limited: England.
Good. Encryption: AES versus Triple-DES. Web.
Internet.com. (2011). Triple des. Web.
Ryan, M.D. (2008). Public-key cryptography. Web.
Tropical Software. Triple des encryption. Web.
wiseGEEK. (2011). What is online banking?. Web.