From b7713cce26cc37a979ebafa02634d5518e0feeb0 Mon Sep 17 00:00:00 2001 From: Sarang Noether <32460187+SarangNoether@users.noreply.github.com> Date: Thu, 17 Dec 2020 17:38:43 -0500 Subject: [PATCH] Precompute initial transcript hash --- src/ringct/bulletproofs_plus.cc | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) diff --git a/src/ringct/bulletproofs_plus.cc b/src/ringct/bulletproofs_plus.cc index 5a286ed90..743598b5a 100644 --- a/src/ringct/bulletproofs_plus.cc +++ b/src/ringct/bulletproofs_plus.cc @@ -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 rct::key TWO_SIXTY_FOUR_MINUS_ONE; // 2**64 - 1 + // Initial transcript hash + static rct::key initial_transcript; + static boost::mutex init_mutex; // 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); + // 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; } @@ -479,17 +488,6 @@ namespace rct return epee::span(&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 static rct::key transcript_update(rct::key &transcript, const rct::key &update_0) { @@ -592,7 +590,7 @@ namespace rct try_again: // 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)); // A @@ -851,7 +849,7 @@ try_again: bp_plus_proof_data_t pd; // Reconstruct the challenges - rct::key transcript = transcript_initialize(); + rct::key transcript = copy(initial_transcript); transcript = transcript_update(transcript, rct::hash_to_scalar(proof.V)); pd.y = transcript_update(transcript, proof.A); CHECK_AND_ASSERT_MES(!(pd.y == rct::zero()), false, "y == 0");