unsigned char foo[4] = "abcd" is not valid C++ because the string
literal "abcd" does not fit into foo due to the terminating NUL
character. This is valid in C, it will just omit the NUL character.
Fixes#962.
Varlen message support for the default sign function comes from recommending
tagged_sha256. sign_custom on the other hand gets the ability to directly sign
message of any length. This also implies signing and verification support for
the empty message (NULL) with msglen 0.
Tests for variable lengths follow in a later commit.
This makes the default sign function easier to use while allowing more granular
control through sign_custom.
Tests for sign_custom follow in a later commit.
This commit adds test coverage including Cirrus scripts, Valgrind
constant time tests for secret data, API tests, nonce function tests,
and test vectors from the spec.
This commit adds the ECDSA adaptor signature APIs:
- Encrypted Signing
Creates an adaptor signature, which includes a proof to verify the adaptor
signature.
- Encryption Verification
Verifies that the adaptor decryption key can be extracted from the adaptor
signature and the completed ECDSA signature.
- Signature Decryption
Derives an ECDSA signature from an adaptor signature and an adaptor decryption
key.
- Key Recovery
Extracts the adaptor decryption key from the complete signature and the adaptor
signature.
This commit adds proving and verification functions for discrete
logarithm equality.
From the spec (https://github.com/discreetlogcontracts/dlcspecs/pull/114):
"As part of the ECDSA adaptor signature a proof of discrete logarithm
equality must be provided. This is a proof that the discrete logarithm of
some X to the standard base G is the same as the discrete logarithm of
some Z to the base Y. This proof can be constructed by using equality
composition on two Sigma protocols proving knowledge of the discrete
logarithm between both pairs of points. In other words the prover proves
knowledge of a such that X = a * G and b such that Z = b * Y and that
a = b. We make the resulting Sigma protocol non-interactive by applying
the Fiat-Shamir transformation with SHA256 as the challenge hash."
This commit adds a nonce function that will be used by default
for ECDSA adaptor signatures.
This nonce function is similar to secp256k1_nonce_function_hardened
except it uses the compressed 33-byte encoding for the pubkey argument.
We need 33 bytes instead of 32 because, unlike with BIP-340, an ECDSA
X-coordinate alone is not sufficient to disambiguate the Y-coordinate.
This will fix the following compile error on macOS
In file included from src/num.h:17,
from src/num_impl.h:14,
from src/bench_whitelist.c:14:
src/num_gmp.h:10:10: fatal error: gmp.h: No such file or directory
33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06 Add secret key extraction from keypair to constant time tests (Elichai Turkel)
36d9dc1e8e6e3b15d805f04c973a8784a78880f6 Add seckey extraction from keypair to the extrakeys tests (Elichai Turkel)
fc96aa73f5c7f62452847a31821890ff1f72a5a4 Add a function to extract the secretkey from a keypair (Elichai Turkel)
Pull request description:
With schnorrsig if you need to tweak the secret key (for BIP32) you must use the keypair API to get compatible secret/public keys which you do by calling `secp256k1_keypair_xonly_tweak_add()`, but after that there's no currently a way to extract the secret key back for storage.
so I added a `secp256k1_keypair_seckey` function to extract the key
ACKs for top commit:
jonasnick:
ACK 33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06
real-or-random:
ACK 33cb3c2b1fc3f3fe46c6d0eab118248ea86c1f06 code inspection, tests pass
Tree-SHA512: 11212db38c8b87a87e2dc35c4d6993716867b45215b94b20522b1b3164ca63d4c6bf5192a6bff0e9267b333779cc8164844c56669a94e9be72df9ef025ffcfd4
1. using xonly_pubkeys in MuSig for input public keys and the combined
pk. For that to work we need to store whether the MuSig aggregated point
has an even y in the session, may need to negate each signers secret
key and may need to negate each signers public key in
musig_partial_sig_verify.
2. using a tagged hash for the message hash.
3. use !fe_is_odd in place of fe_is_quad_var
As identified in #829 and #833. Fixes#829.
Since we touch this anyway, this commit additionally makes the
identifiers in the benchmark files a little bit more consistent.
