CAPEC-485 Detail

An attacker obtains an authoritative or reputable signer's private signature key by exploiting a cryptographic weakness in the signature algorithm or pseudorandom number generation and then uses this key to forge signatures from the original signer to mislead a victim into performing actions that benefit the attacker.

Prerequisites

An authoritative signer is using a weak method of random number generation or weak signing software that causes key leakage or permits key inference.
An authoritative signer is using a signature algorithm with a direct weakness or with poorly chosen parameters that enable the key to be recovered using signatures from that signer.

Skills Required

Cryptanalysis of signature generation algorithm
Reverse engineering and cryptanalysis of signature generation algorithm implementation and random number generation
Ability to create malformed data blobs and know how to present them directly or indirectly to a victim.

Mitigations

Ensure cryptographic elements have been sufficiently tested for weaknesses.

Related Weaknesses

References

REF-419

Attacking DSA Under a Repeated Bits Assumption
P.J. Leadbitter, D. Page, N.P. Smart.

REF-420

DSA-1571-1 openssl -- predictable random number generator
Debian Security.

Submission

Modifications