Modernize GHASH: allowing GCM to accept input that is not block-aligned #4469
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randombit
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Dec 21, 2024
Most notably, this lifts the limitation that GHASH::update() requires block-aligned data input by transparently caching non-aligned data using the AlignmentBuffer helper. With that, the GCM mode of operation can stream-process data that is not block aligned. The GMAC used to contain an AlignmentBuffer to handle the same limitation described above. This was removed, as GHASH now handles non-aligned data transparently. Finally, this cleans up the state management of GHASH as much as possible and removes a few public interfaces.
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Most notably, this lifts the limitation that GHASH::update() requires block-aligned data input by transparently caching non-aligned data using the AlignmentBuffer helper. With that, the GCM mode of operation can stream-process data that is not block aligned.
The GMAC used to contain an AlignmentBuffer to handle the same limitation described above. This was removed, as GHASH now handles non-aligned data transparently.
Finally, this cleans up the state management of GHASH as much as possible and removes a few public interfaces.