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Precompute initial transcript hash

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Sarang Noether 2020-12-17 17:38:43 -05:00 committed by moneromooo-monero
parent bd27debb2d
commit b7713cce26
1 changed files with 11 additions and 13 deletions
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24
src/ringct/bulletproofs_plus.cc
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@ -81,6 +81,9 @@ namespace rct
static const rct::key MINUS_INV_EIGHT = { { 0x74, 0xa4, 0x19, 0x7a, 0xf0, 0x7d, 0x0b, 0xf7, 0x05, 0xc2, 0xda, 0x25, 0x2b, 0x5c, 0x0b, 0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a } }; // -(8**(-1)) static const rct::key MINUS_INV_EIGHT = { { 0x74, 0xa4, 0x19, 0x7a, 0xf0, 0x7d, 0x0b, 0xf7, 0x05, 0xc2, 0xda, 0x25, 0x2b, 0x5c, 0x0b, 0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a } }; // -(8**(-1))
static rct::key TWO_SIXTY_FOUR_MINUS_ONE; // 2**64 - 1 static rct::key TWO_SIXTY_FOUR_MINUS_ONE; // 2**64 - 1
// Initial transcript hash
static rct::key initial_transcript;
static boost::mutex init_mutex; static boost::mutex init_mutex;
// Use the generator caches to compute a multiscalar multiplication // Use the generator caches to compute a multiscalar multiplication
@ -150,6 +153,12 @@ namespace rct
} }
sc_sub(TWO_SIXTY_FOUR_MINUS_ONE.bytes, TWO_SIXTY_FOUR_MINUS_ONE.bytes, ONE.bytes); sc_sub(TWO_SIXTY_FOUR_MINUS_ONE.bytes, TWO_SIXTY_FOUR_MINUS_ONE.bytes, ONE.bytes);
// Generate the initial Fiat-Shamir transcript hash, which is constant across all proofs
static const std::string domain_separator(config::HASH_KEY_BULLETPROOF_PLUS_TRANSCRIPT);
ge_p3 initial_transcript_p3;
rct::hash_to_p3(initial_transcript_p3, rct::hash2rct(crypto::cn_fast_hash(domain_separator.data(), domain_separator.size())));
ge_p3_tobytes(initial_transcript.bytes, &initial_transcript_p3);
init_done = true; init_done = true;
} }
@ -479,17 +488,6 @@ namespace rct
return epee::span<const rct::key>(&a[start], stop - start); return epee::span<const rct::key>(&a[start], stop - start);
} }
// Initialize the Fiat-Shamir transcript
static rct::key transcript_initialize()
{
static const std::string domain_separator(config::HASH_KEY_BULLETPROOF_PLUS_TRANSCRIPT);
rct::key transcript;
ge_p3 transcript_p3;
rct::hash_to_p3(transcript_p3, rct::hash2rct(crypto::cn_fast_hash(domain_separator.data(), domain_separator.size())));
ge_p3_tobytes(transcript.bytes, &transcript_p3);
return transcript;
}
// Update the transcript // Update the transcript
static rct::key transcript_update(rct::key &transcript, const rct::key &update_0) static rct::key transcript_update(rct::key &transcript, const rct::key &update_0)
{ {
@ -592,7 +590,7 @@ namespace rct
try_again: try_again:
// This is a Fiat-Shamir transcript // This is a Fiat-Shamir transcript
rct::key transcript = transcript_initialize(); rct::key transcript = copy(initial_transcript);
transcript = transcript_update(transcript, rct::hash_to_scalar(V)); transcript = transcript_update(transcript, rct::hash_to_scalar(V));
// A // A
@ -851,7 +849,7 @@ try_again:
bp_plus_proof_data_t pd; bp_plus_proof_data_t pd;
// Reconstruct the challenges // Reconstruct the challenges
rct::key transcript = transcript_initialize(); rct::key transcript = copy(initial_transcript);
transcript = transcript_update(transcript, rct::hash_to_scalar(proof.V)); transcript = transcript_update(transcript, rct::hash_to_scalar(proof.V));
pd.y = transcript_update(transcript, proof.A); pd.y = transcript_update(transcript, proof.A);
CHECK_AND_ASSERT_MES(!(pd.y == rct::zero()), false, "y == 0"); CHECK_AND_ASSERT_MES(!(pd.y == rct::zero()), false, "y == 0");