Distinguishing Attack on MAC with Enveloped Method Using MD5

The MAC with enveloped method using MD5 is recommended as an Internet proposed standard RFC 1828. So far no distinguishing attack on it is presented. In this paper, we firstly proposes an adaptive chosen message distinguishing attack on the MAC with enveloped method using MD5, of which the time complexity and data complexity are both 2⁹⁶ and table size is 2⁸⁹ with a success rate 0.87. Then we relax the adaptive chosen message distinguishing attack to a chosen message distinguishing attack, of which the data complexity is increased to 2¹¹³, but the table size is reduced to 2⁶⁶ with the same success rate.