PRF ⇒ MAC

A PRF implies a MAC.

Construction

Migrated verbatim from PRF § Other results:

PRF implies MAC: $\mathsf{Tag}(k,m)=\mathsf{PRF}(k,m)$ is a secure one-time MAC; extending to many messages uses standard domain-extension techniques

Notes

status: stub and source: folklore: the claim carried no citation on the page it was migrated from, and none was invented.

Suspected imprecision in the migrated sketch, recorded and not fixed. $\mathsf{Tag}(k,m)=\mathsf{PRF}(k,m)$ is a secure many-time (EUF-CMA) fixed-length MAC, not merely a one-time MAC; the one-time qualifier understates the standard result. The following clause also conflates message count with message length — domain extension buys long messages, not more queries.