There is No Need to Waste Communication Bandwidth on MACs.

We address the problem of detecting data corruption in computer and device communications without generating, transmitting or verifying integrity metadata. Such metadata typically hold mathematical summaries of the content which is being transmitted, such as checksums, Integrity Check Values (ICVs) or Message Authentication Codes (MACs), and are costly to generate and transmit. In the paper we discuss a data integrity methodology, which is alternative to MACs or ICVs, and is based on a novel concept of ‘implicit integrity’. Implicit integrity supports the detection of corruption based on the observation that regular unencrypted user data typically exhibit patterns, such as repeated bytes words etc. When some encrypted content becomes corrupted and is decrypted, it no longer exhibits patterns. It is the absence or presence of patterns in decrypted content which denotes whether some content is modified or not. In the paper we summarize some of our findings including discovered entropy properties of server and client data, security bounds associated with implicit integrity and proposals for constructions that are practical and can be used in communication systems, supporting implicit integrity at low cost.