diff options
author | René Meusel <[email protected]> | 2017-04-13 11:26:13 +0200 |
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committer | René Meusel <[email protected]> | 2017-04-13 11:26:13 +0200 |
commit | 95a23a75356553e7172a2b45162c90d1c38ea881 (patch) | |
tree | f89caaf02e995481de57ab3ac0362d013ceb09cb /src/lib/stream/ctr/ctr.cpp | |
parent | bf1240ccba31e77cff5f09a11af904bedcd0e25a (diff) |
Refactor: remove big-endian addition code duplication
Diffstat (limited to 'src/lib/stream/ctr/ctr.cpp')
-rw-r--r-- | src/lib/stream/ctr/ctr.cpp | 44 |
1 files changed, 26 insertions, 18 deletions
diff --git a/src/lib/stream/ctr/ctr.cpp b/src/lib/stream/ctr/ctr.cpp index b56923324..9ab1a38c2 100644 --- a/src/lib/stream/ctr/ctr.cpp +++ b/src/lib/stream/ctr/ctr.cpp @@ -87,20 +87,30 @@ void CTR_BE::increment_counter() const size_t bs = m_cipher->block_size(); const size_t n_wide = m_counter.size() / bs; + add_counter(n_wide); + + m_cipher->encrypt_n(m_counter.data(), m_pad.data(), n_wide); + m_pad_pos = 0; + } + +void CTR_BE::add_counter(const uint64_t counter) + { + const size_t bs = m_cipher->block_size(); + const size_t n_wide = m_counter.size() / bs; + for(size_t i = 0; i != n_wide; ++i) { - uint16_t carry = static_cast<uint16_t>(n_wide); - for(size_t j = 0; carry && j != m_ctr_size; ++j) + uint64_t local_counter = counter; + uint16_t carry = static_cast<uint8_t>(local_counter); + for(size_t j = 0; (carry || local_counter) && j != m_ctr_size; ++j) { const size_t off = i*bs + (bs-1-j); const uint16_t cnt = static_cast<uint16_t>(m_counter[off]) + carry; m_counter[off] = static_cast<uint8_t>(cnt); - carry = (cnt >> 8); + local_counter = (local_counter >> 8); + carry = (cnt >> 8) + static_cast<uint8_t>(local_counter); } } - - m_cipher->encrypt_n(m_counter.data(), m_pad.data(), n_wide); - m_pad_pos = 0; } void CTR_BE::seek(uint64_t offset) @@ -110,23 +120,21 @@ void CTR_BE::seek(uint64_t offset) const uint64_t base_counter = n_wide * (offset / m_counter.size()); zeroise(m_counter); + buffer_insert(m_counter, 0, m_iv); - for (size_t i = 0; i != n_wide; ++i) + // Set m_counter blocks to IV, IV + 1, ... IV + n + for(size_t i = 1; i != n_wide; ++i) { - buffer_insert(m_counter, bs * i, m_iv); + buffer_insert(m_counter, i*bs, &m_counter[(i-1)*bs], bs); - uint64_t counter = base_counter + i; - uint16_t carry = static_cast<uint8_t>(counter); - for (size_t j = 0; (carry || counter) && j != m_ctr_size; ++j) - { - const size_t off = i*bs + (bs-1-j); - const uint16_t cnt = static_cast<uint16_t>(m_counter[off]) + carry; - m_counter[off] = static_cast<uint8_t>(cnt); - counter = (counter >> 8); - carry = (cnt >> 8) + static_cast<uint8_t>(counter); - } + for(size_t j = 0; j != m_ctr_size; ++j) + if(++m_counter[i*bs + (bs - 1 - j)]) + break; } + if (base_counter > 0) + add_counter(base_counter); + m_cipher->encrypt_n(m_counter.data(), m_pad.data(), n_wide); m_pad_pos = offset % m_counter.size(); } |