Contributed by jcr on from the the-poly-cha-cha-is-the-new-dance-craze dept.
OpenBSD developer Damien Miller (djm@) wrote a great post titled "ChaCha20 and Poly1305 in OpenSSH" and below is a small excerpt:
Recently, I committed support for a new authenticated encryption cipher for OpenSSH, firstname.lastname@example.org. This cipher combines two primitives from Daniel J. Bernstein: the ChaCha20 cipher and the Poly1305 MAC (Message Authentication Code) and was inspired by Adam Langley's similar proposal for TLS.
Why another cipher and MAC? A few reasons... First, we would like a high-performance cipher to replace RC4 since it is pretty close to broken now, we'd also like an authenticated encryption mode to complement AES-GCM - which is great if your hardware supports it, but takes significant voodoo to make run in constant time and, finally, having an authenticated encryption mode that is based on a stream cipher allows us to encrypt the packet lengths again.
Wait, what do you mean by "encrypt the packet lengths again"? (last rhetorical question, I promise) Well, it's a long story that requires a little background...
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