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74f66bb5c3
Calling mbedtls_mpi_cmp_int reveals the number of leading zero limbs to an adversary who is capable of very fine-grained timing measurements. This is very little information, but could be practical with secp521r1 (1/512 chance of the leading limb being 0) if the adversary can measure the precise timing of a large number of signature operations. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
8 lines
401 B
Plaintext
8 lines
401 B
Plaintext
Security
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* Fix a potential side channel vulnerability in ECDSA ephemeral key generation.
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An adversary who is capable of very precise timing measurements could
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learn partial information about the leading bits of the nonce used for the
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signature, allowing the recovery of the private key after observing a
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large number of signature operations. This completes a partial fix in
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Mbed TLS 2.20.0.
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