secp: context randomize in a few places - #1594
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Side-channel hardening: pass a fresh 32-byte GetStrongRandBytes seed to secp256k1_context_randomize immediately after context creation, matching the randomization of secp256k1_context_sign in key.cpp. No change to consensus behavior or key/signature formats.
Side-channel hardening: blind each SIGN-capable secp256k1 context in the wallet with a fresh 32-byte GetRandBytes seed via secp256k1_context_randomize, mirroring key.cpp ECC_Start. Assert on null ctx and on a 0 randomize return. No consensus impact.
Force BPPP, ECDSA_ADAPTOR, ECDSA_S2C, and SCHNORRSIG_HALFAGG OFF alongside the existing MUSIG OFF in src/CMakeLists.txt. These experimental modules default to ON in libsecp256k1's CMake but have zero references in the Elements tree; building them is dead code that enlarges the binary and attack surface. Genuinely used modules (ECDH, RECOVERY, EXTRAKEYS, SCHNORRSIG, ELLSWIFT, GENERATOR, RANGEPROOF, SURJECTIONPROOF, WHITELIST) remain enabled.
The wallet Schnorr-signing path passed uint256{} (all-zero) as aux_rnd, a
side-channel/key-reuse hazard. Draw a fresh strong-random aux_rnd per sign.
Adjust the upstream BIP341 key-path vector test to sign deterministically via
key.SignSchnorr with the zero aux the vectors encode, since CreateSchnorrSig
randomness makes exact-hex reproduction impossible.
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utACK. Only reviewed the total diff in the Github UI. It's a worthwhile change IMHO. But I assume you weighed this defense-in-depth against causing potential rebase conflicts. |
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Adds a few instances of
secp256k1_context_randomizein areas where we are using the secp context