sha256.hpp

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// === AUDIT STATUS ===
// internal:    { status: Complete, auditors: [Luke], commit: }
// external_1:  { status: not started, auditors: [], commit: }
// external_2:  { status: not started, auditors: [], commit: }
// =====================
 
#pragma once
#include "barretenberg/stdlib_circuit_builders/plookup_tables/plookup_tables.hpp"
#include <array>
 
#include "barretenberg/numeric/bitop/sparse_form.hpp"
#include "barretenberg/stdlib/primitives/circuit_builders/circuit_builders_fwd.hpp"
 
#include "../../primitives/field/field.hpp"
 
namespace bb::stdlib {
 
template <typename Builder> class SHA256 {
 
    using field_ct = field_t<Builder>;
 
    static constexpr fr base{ 16 };
 
    static constexpr std::array<fr, 4> left_multipliers{
        base.pow(32 - 7) + base.pow(32 - 18),                         // limb 0: rot7 + rot18
        base.pow(32 - 18 + 3) + fr(1),                                // limb 1: rot18 + shift3
        base.pow(10 - 7) + base.pow(32 - 18 + 10) + base.pow(10 - 3), // limb 2: rot7 + rot18 + shift3
        base.pow(18 - 7) + fr(1) + base.pow(18 - 3),                  // limb 3: rot7 + rot18 + shift3
    };
 
    static constexpr std::array<fr, 4> right_multipliers{
        base.pow(32 - 17) + base.pow(32 - 19),         // limb 0: rot17 + rot19
        base.pow(32 - 17 + 3) + base.pow(32 - 19 + 3), // limb 1: rot17 + rot19
        base.pow(32 - 19 + 10) + fr(1),                // limb 2: rot19 + shift10
        base.pow(18 - 17) + base.pow(18 - 10),         // limb 3: rot17 + shift10
    };
 
    static constexpr std::array<uint64_t, 64> round_constants{
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
    };
    struct sparse_witness_limbs {
        sparse_witness_limbs(const field_ct& in = 0)
            : normal(in)
        {}
        sparse_witness_limbs(const sparse_witness_limbs& other) = default;
        sparse_witness_limbs(sparse_witness_limbs&& other) = default;
        sparse_witness_limbs& operator=(const sparse_witness_limbs& other) = default;
        sparse_witness_limbs& operator=(sparse_witness_limbs&& other) = default;
        ~sparse_witness_limbs() = default;
 
        field_ct normal;
 
        std::array<field_ct, 4> sparse_limbs;
 
        std::array<field_ct, 4> rotated_limb_corrections;
 
        bool has_sparse_limbs = false;
    };
    struct sparse_value {
        sparse_value(const field_ct& in = 0)
            : normal(in)
        {
            if (normal.is_constant()) {
                sparse = field_ct(in.get_context(),
                                  bb::fr(numeric::map_into_sparse_form<16>(uint256_t(in.get_value()).data[0])));
            }
        }
 
        sparse_value(const sparse_value& other) = default;
        sparse_value(sparse_value&& other) = default;
        sparse_value& operator=(const sparse_value& other) = default;
        sparse_value& operator=(sparse_value&& other) = default;
        ~sparse_value() = default;
 
        field_ct normal;
        field_ct sparse;
    };
 
    static sparse_witness_limbs convert_witness(const field_ct& input);
 
    static field_ct choose_with_sigma1(sparse_value& e, const sparse_value& f, const sparse_value& g);
 
    static field_ct majority_with_sigma0(sparse_value& a, const sparse_value& b, const sparse_value& c);
    static sparse_value map_into_choose_sparse_form(const field_ct& input);
    static sparse_value map_into_maj_sparse_form(const field_ct& input);
 
    static field_ct add_normalize(const field_ct& a, const field_ct& b);
 
  public:
    static std::array<field_ct, 8> sha256_block(const std::array<field_ct, 8>& h_init,
                                                const std::array<field_ct, 16>& input);
 
    static std::array<field_ct, 64> extend_witness(const std::array<field_ct, 16>& w_in);
};
} // namespace bb::stdlib