System and method for variable length encryption
Systems and methods for performing a secure transaction provided. In one embodiment, the method includes: reading data on a command token, reading data on a token; encrypting the token data with a key; encrypting an authentication data with a clear text token data; and transmitting the encrypted authentication data with the encrypted token data to a remote device.
1. A method of encrypting token data at a token reader comprising a processor, the method comprising the token reader:
receiving clear text token data from a token;
selecting a symbol set corresponding to the clear text token data, wherein the symbol set is an arbitrary string symbol set comprising a plurality of members, wherein each of the plurality of members represents a data element in the clear text token data;
defining a first portion and a second portion of the clear text token data;
generating an encryption mask based on encrypting the second portion of the clear text token data using a key; and
encrypting the clear text data by applying the encryption mask to the first portion using a modulo operation while not encrypting the second portion, thereby resulting in encrypted token data comprising an encrypted first portion and an unencrypted second portion;
wherein the encrypted token data has the same format and length as the clear text token data, and uses the same symbol set as the clear text token data.
2. The method of claim 1 , wherein the modulo operation is a modulo addition.
3. The method of claim 1 , wherein the modulo operation is a modulo subtraction.
4. The method of claim 1 , wherein the clear text token data comprises a primary account number (PANS).
5. The method of claim 4 , wherein the clear text token data comprises discretionary data.
6. The method of claim 1 , wherein the arbitrary string symbol set comprises 26 characters that represent letters of an alphabet and wherein the modulo operation is a modulo 26 operation.
7. The method of claim 1 , wherein encrypting the second portion using the key involves a multi-alphabet string cipher.
8. The method of claim 1 , further comprising the token reader transmitting the encrypted token data to a remote device over a network.
9. The method of claim 8 , wherein the network is a public network.
10. The method of claim 1 , wherein the token reader is a point-of-sale terminal and the clear text token data comprises bank card data.
11. The method of claim 1 , further comprising the token reader translating the first portion of the clear text token data prior to encrypting the first portion of the token data, and wherein encrypting the first portion of the clear text token data comprises encrypting the translated first portion of the clear text token data by applying the encryption mask.
12. The method of claim 11 , wherein translating the first portion of the clear text token data comprises substitution.
13. The method of claim 1 , wherein the received clear text token data is clear text token data from a bank card, and wherein the first portion of the clear text token data comprises a portion of an account number, and the second portion of the clear text token data comprises a bank identification number.
14. The method of claim 13 , wherein the encryption mask is created by encrypting the bank identification number.
15. A method of decrypting encrypted token data at a secure transaction device comprising a network interface coupled to a transaction processing network, the method comprising the secure transaction device:
receiving encrypted token data over the transaction processing network;
selecting a symbol set used to encrypt clear text token data to encrypted token data, wherein the symbol set is an arbitrary string symbol set comprising a plurality of members, wherein each of the plurality of members represents a data element in the clear text token data;
defining a first portion and a second portion of the encrypted token data, where the encrypted token data comprises an encrypted first portion and an unencrypted second portion;
generating an encryption mask based on encrypting the second portion of the encrypted token data using a key; and
decrypting the encrypted token data by applying the encryption mask to the first portion using a modulo operation, thereby resulting in clear text token data comprising a decrypted first portion and an unencrypted second portion;
wherein the encrypted token data has the same format and length as the clear text token data, and uses the same symbol set as the clear text token data.
16. The method of claim 15 , wherein the modulo operation is a modulo addition.
17. The method of claim 15 , wherein the modulo operation is a modulo subtraction.
18. The method of claim 15 , wherein the modulo operation is complementary to a second modulo operation used during the encryption of the clear text token data to encrypted token data.
19. The method of claim 15 , wherein the received clear text token data is clear text token data from a bank card, and wherein the decrypted first portion of the clear text token data comprises a portion of an account number, and the unencrypted second portion of the clear text token data comprises a bank identification number.
20. The method of claim 19 , wherein the encryption mask is generated by encrypting the bank identification number.