On the security of two MAC algorithms

  • Authors:
  • Bart Preneel;Paul C. Van Oorschot

  • Affiliations:
  • Katholieke Universiteit Leuven, Dept. Electrical Engineering-ESAT, Heverlee, Belgium;Bell-Northern Research, Ottawa, Ontario, Canada

  • Venue:
  • EUROCRYPT'96 Proceedings of the 15th annual international conference on Theory and application of cryptographic techniques
  • Year:
  • 1996

Quantified Score

Hi-index 0.00

Visualization

Abstract

The security of two message authentication code (MAC) algorithms is considered: the MD5-based envelope method (RFC 1828), and the banking standard MAA (ISO 8731-2). Customization of a general MAC forgery attack allows improvements in both cases. For the envelope method, the forgery attack is extended to allow key recovery; for example, a 128-bit key can be recovered using 267 known text-MAC pairs and time plus 213 chosen texts. For MAA, internal collisions are feud with fewer and shorter messages than previously by exploiting the algorithm's internal structure; consequently, the number of chosen texts (each 256 Kbyte long) for a forgery can be reduced by two orders of magnitude, e.g. from 224 to 217. This attack can be extended to one requiring only short messages (224 messages shorter than 1 Kbyte) to circumvent the special MAA mode for long messages. Moreover, certain internal collisions allow key recovery, and weak keys for MAA are identified.