FREAK

cryptographysecurity

A 2015 attack forcing servers to use weak, factorable export-grade RSA keys.

Factoring RSA Export Keys exploited leftover 1990s export ciphers: an attacker could force a downgrade to 512-bit RSA, factor the key, and impersonate the server. It was a direct legacy of old US crypto export restrictions.

FREAK exploited export-grade cryptography: deliberately weakened cipher suites created in the 1990s to satisfy United States export restrictions on strong encryption, using key sizes small enough to be broken. The restrictions were lifted long before, and the code supporting the weak suites remained in widely used implementations.

The attack forced a client and server that both supported strong cryptography to negotiate an export-grade suite, whose key could then be factored cheaply. The vulnerability was not in the strong cryptography anyone was using; it was in the continued presence of a mode nobody had used in fifteen years and nobody had removed.

That is the policy lesson and it is the reason FREAK is cited in every subsequent debate about lawful access. A deliberate weakness introduced for a government requirement outlived the requirement by more than a decade and was then turned against the people it was meant to protect. Anyone proposing exceptional access to encryption is proposing to create exactly this kind of artefact, and the historical record on how long such artefacts persist is not encouraging.

Also known as: FREAK, Factoring RSA Export Keys, CVE-2015-0204

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