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Matt Caswell authored
Keegan Ryan (NCC Group) has demonstrated a side channel attack on an ECDSA signature operation. During signing the signer calculates: s:= k^-1 * (m + r * priv_key) mod order The addition operation above provides a sufficient signal for a flush+reload attack to derive the private key given sufficient signature operations. As a mitigation (based on a suggestion from Keegan) we add blinding to the operation so that: s := k^-1 * blind^-1 (blind * m + blind * r * priv_key) mod order Since this attack is a localhost side channel only no CVE is assigned. Reviewed-by: Rich Salz <rsalz@openssl.org>
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