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ellswift: don't declassify or leave sk in sha256 buffer #1863

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ellswift: don't declassify or leave sk in sha256 buffer #1863

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3 changes: 2 additions & 1 deletion src/modules/ellswift/main_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -454,7 +454,7 @@ int secp256k1_ellswift_create(const secp256k1_context *ctx, unsigned char *ell64
secp256k1_ellswift_sha256_init_create(&hash);
secp256k1_sha256_write(secp256k1_get_hash_context(ctx), &hash, seckey32, 32);
secp256k1_sha256_write(secp256k1_get_hash_context(ctx), &hash, zero32, sizeof(zero32));
secp256k1_declassify(ctx, &hash, sizeof(hash)); /* private key is hashed now */
secp256k1_declassify(ctx, &hash.s, sizeof(hash.s)); /* The private key has been hashed, but sk remains in the buffer */
if (auxrnd32) secp256k1_sha256_write(secp256k1_get_hash_context(ctx), &hash, auxrnd32, 32);

/* Compute ElligatorSwift encoding and construct output. */
Expand All @@ -463,6 +463,7 @@ int secp256k1_ellswift_create(const secp256k1_context *ctx, unsigned char *ell64

secp256k1_memczero(ell64, 64, !ret);
secp256k1_scalar_clear(&seckey_scalar);
secp256k1_sha256_clear(&hash);

return ret;
}
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