precompile_crypto.lua

-- Cryptographic implementations for EVM precompiles
-- This file contains implementations of cryptographic functions needed for precompiles

-- SHA-256 implementation in pure Lua
-- Based on the SHA-256 specification (FIPS 180-4)

local function sha256_init()
    return {
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
    }
end

local sha256_k = {
    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
}

local function rotr(n, b)
    local s = n >> b
    local t = n << (32 - b)
    return (s | t) & 0xFFFFFFFF
end

local function sha256_process_block(state, block)
    local w = {}
    
    -- Prepare message schedule
    for i = 0, 15 do
        w[i] = (block[i*4+1] << 24) | (block[i*4+2] << 16) | (block[i*4+3] << 8) | block[i*4+4]
    end
    
    for i = 16, 63 do
        local s0 = rotr(w[i-15], 7) ~ rotr(w[i-15], 18) ~ (w[i-15] >> 3)
        local s1 = rotr(w[i-2], 17) ~ rotr(w[i-2], 19) ~ (w[i-2] >> 10)
        w[i] = (w[i-16] + s0 + w[i-7] + s1) & 0xFFFFFFFF
    end
    
    -- Initialize working variables
    local a, b, c, d, e, f, g, h = state[1], state[2], state[3], state[4], state[5], state[6], state[7], state[8]
    
    -- Main loop
    for i = 0, 63 do
        local S1 = rotr(e, 6) ~ rotr(e, 11) ~ rotr(e, 25)
        local ch = (e & f) ~ ((~e) & g)
        local temp1 = (h + S1 + ch + sha256_k[i+1] + w[i]) & 0xFFFFFFFF
        local S0 = rotr(a, 2) ~ rotr(a, 13) ~ rotr(a, 22)
        local maj = (a & b) ~ (a & c) ~ (b & c)
        local temp2 = (S0 + maj) & 0xFFFFFFFF
        
        h = g
        g = f
        f = e
        e = (d + temp1) & 0xFFFFFFFF
        d = c
        c = b
        b = a
        a = (temp1 + temp2) & 0xFFFFFFFF
    end
    
    -- Update state
    state[1] = (state[1] + a) & 0xFFFFFFFF
    state[2] = (state[2] + b) & 0xFFFFFFFF
    state[3] = (state[3] + c) & 0xFFFFFFFF
    state[4] = (state[4] + d) & 0xFFFFFFFF
    state[5] = (state[5] + e) & 0xFFFFFFFF
    state[6] = (state[6] + f) & 0xFFFFFFFF
    state[7] = (state[7] + g) & 0xFFFFFFFF
    state[8] = (state[8] + h) & 0xFFFFFFFF
end

local function sha256(data)
    local state = sha256_init()
    local len = #data
    local padded = {}
    
    -- Copy data
    for i = 1, len do
        padded[i] = data[i]
    end
    
    -- Append padding
    padded[len + 1] = 0x80
    
    -- Pad to 56 bytes mod 64
    local pad_len = (56 - (len + 1) % 64) % 64
    for i = 1, pad_len do
        padded[len + 1 + i] = 0
    end
    
    -- Append length in bits as 64-bit big-endian
    local bit_len = len * 8
    for i = 7, 0, -1 do
        padded[#padded + 1] = (bit_len >> (i * 8)) & 0xFF
    end
    
    -- Process blocks
    for i = 1, #padded, 64 do
        local block = {}
        for j = 0, 63 do
            block[j + 1] = padded[i + j] or 0
        end
        sha256_process_block(state, block)
    end
    
    -- Convert state to bytes
    local result = {}
    for i = 1, 8 do
        result[(i-1)*4 + 1] = (state[i] >> 24) & 0xFF
        result[(i-1)*4 + 2] = (state[i] >> 16) & 0xFF
        result[(i-1)*4 + 3] = (state[i] >> 8) & 0xFF
        result[(i-1)*4 + 4] = state[i] & 0xFF
    end
    
    return result
end

return {
    sha256 = sha256
}