Add blinding to an ECDSA signature
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>
parent
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