ssh-keygen fails to create RSA keys of length in bits not dividable by 8

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Environment

SUSE Linux Enterprise Server 11 SP3
SUSE Linux Enterprise Server 11 SP2

Situation

Running ssh-keygen with an "odd" (not dividable by 8) key length may fail without further explanation in FIPS mode:

$ ssh-keygen -v -b 2049 -t rsa -N "1234" -f testkey.rsa
Generating public/private rsa key pair.
rsa_generate_private_key: key generation failed.
$

Resolution

Use an RSA key length dividable by 256 as defined by ANSI X9.31.

Cause

According to ANSI X9.31, the length of an RSA key must be a multiple of 32 bytes, or 256 bits. Keys having a length that is not a multiple of 8 bits do not work and fail the FIPS RSA key validation of OpenSSL 0.9.8j.

Disclaimer

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