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Encryption Transaction with 3DES. Team W2 Yervant Dermenjian (W21) Taewan Kim (W22) Evan Mengstab (W23) Xiaochun Zhu (W24) . Objective: To implement a secure credit card transaction using 3DES encryption using Kerberos-style authentication. Team Manager: Rebecca Miller.
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Encryption Transaction with 3DES Team W2 Yervant Dermenjian (W21)Taewan Kim (W22) Evan Mengstab (W23) Xiaochun Zhu (W24) Objective: To implement a secure credit card transaction using 3DES encryption using Kerberos-style authentication. Team Manager: Rebecca Miller Current Stage: Design Proposal 01/21/2004
What’s Wrong with Credit Purchases? • Point-of-sale terminals transmit your name, credit card number, and expiration dates ‘in the clear’ (unencrypted). • Using Kerberos-style authentication, we can transmit encrypted information that can be verified by the card authorizer without actually containing sensitive information.
Triple Data Encryption Standard • Difficult to decipher for large encryption keys • Symmetric Key Cipher – encryption & decryption use same key • Based on DES – a very trusted cipher • Encryption utilized in new ATMs • Free to use • Accepted as the new standard for federal agencies in 1999
Kerberos-style Authentication • Provides authentication without transmitting sensitive information. • Encrypt card expiration date using credit card number and secret PIN as encryption key. • The data payload is arbitrary. Only the cardholder and card acquirer have the key.
How It Works • Transmit: name, merchant, price, encrypted expiration date • Card company has cc# and PIN to decrypt packet • If expiration date matches, purchase is approved • CC# and PIN are never transmitted, but essential to authenticate
Security In Making Purchases • Identity theft is a growing problem • Sensitive information never transmitted • Uses existing cards and phone network • Credit and charge card fraud costs cardholders and issuers hundreds of millions of dollars each year
Design Diagram Input 100 Name Reg b’100 CC# Reg b’54 68 Output Concatenate 3DES encryption of Expiration Date using PIN+CC# Key PIN Reg b’14 11 Package Packager Pin+CC# = Encryption Key ExpDate Reg b’11 MerchID-Name-Payload-Price 11 25 MerchID b’25 12 MerchPrice b’12
Current Status • Block Diagram breakdown of functions • Decisions on packet encryption (100%) • Analysis of 3DES algorithm (10%) • C Language software implementation of encryption and decryption (0%) • Verilog HDL (0%) • Verilog Gate-level design (0%) • Schematic Representation (0%) • Chip Layout (0%) • SPICE Simulation (0%)
Design Decisions • Cardholder’s name encoded in shortened ASCII, only 32 letters (4 bytes). • Merchant ID shortened to 5 letters. • Merchandise Cost capped at $4,096 (12 bits) • Credit Card number and PIN concatenated as key. Longer key -> Stronger encryption. • Transmitted data • Unencrypted: Cardholder’s name, Merchant’s ID, purchase amount • Encrypted: expiration date
Design Alternatives • Rijndael (AES) encryption algorithm • Does not comply with standard for ATMs • Larger silicon area • Clock-synchronized random number key • Incompatible with current credit cards • Difficult to keep smart chip in card synchronized with server
Problems and Questions • Should sensitive data (PIN and CC#) be the encrypted data or the encryption key? • Less secure to encrypt purchase price, creating variable encrypted messages using the same key? • Need a rough transistor count. • Is this encryption difficult to crack but still manageable to realize in hardware?
