Method Decrypt

src/crypto/chacha20poly1305.cpp:83–97

}

bool AEADChaCha20Poly1305::Decrypt(std::span<const std::byte> cipher, std::span<const std::byte> aad, Nonce96 nonce, std::span<std::byte> plain1, std::span<std::byte> plain2) noexcept
{
    assert(cipher.size() == plain1.size() + plain2.size() + EXPANSION);

    // Verify tag (using key drawn from block 0).
    m_chacha20.Seek(nonce, 0);
    std::byte expected_tag[EXPANSION];
    ComputeTag(m_chacha20, aad, cipher.first(cipher.size() - EXPANSION), expected_tag);
    if (timingsafe_bcmp_internal(UCharCast(expected_tag), UCharCast(cipher.last(EXPANSION).data()), EXPANSION)) return false;

    // Decrypt (starting at block 1).
    m_chacha20.Crypt(cipher.first(plain1.size()), plain1);
    m_chacha20.Crypt(cipher.subspan(plain1.size()).first(plain2.size()), plain2);
    return true;
}

void AEADChaCha20Poly1305::Keystream(Nonce96 nonce, std::span<std::byte> keystream) noexcept
{