[Ach] The sad story of lonely AES-CTR

Aaron Zauner azet at azet.org
Tue Dec 17 20:26:24 CET 2013


Does anyone know why OpenSSL 1.0.1e supports AES-CTR as block cipher mode but misses AES-CTR completely in ciphersuites?

As it seems Counter Mode never made it to the RFC: http://tools.ietf.org/html/rfc5288
GCM did.

“If my calculations are correct” AES-CTR would be significantly faster than AES-GCM (since openssl speed does not support benching aes-gcm nor aes-ctr I simply went for a complexity comparison - I should maybe write a real test for that as well).

BTW. Ben Laurie commited an exotic chaining mode called IGE to OpenSSL some time ago:
Infinite Garble Extension (IGE) is a block cipher mode[1]. It has the property
that errors are propagated forward indefinitely. Bi-directional IGE (biIGE)
propogates errors in both directions: that is, any change to the ciphertext will
cause all of the plaintext to be corrupted. 

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