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Merge pull request #704 from ethereum/malleability

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Expanded malleability risks.
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chriseth 2016-07-18 19:34:35 +02:00 committed by GitHub
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docs/security-considerations.rst
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@ -146,7 +146,11 @@ Minor Details
Furthermore, it is not enforced by the EVM, so a contract function that "claims" Furthermore, it is not enforced by the EVM, so a contract function that "claims"
to be constant might still cause changes to the state. to be constant might still cause changes to the state.
- Types that do not occupy the full 32 bytes might contain "dirty higher order bits". - Types that do not occupy the full 32 bytes might contain "dirty higher order bits".
This is especially important if you access ``msg.data`` - it poses a malleability risk. This is especially important if you access ``msg.data`` - it poses a malleability risk:
You can craft transactions that call a function ``f(uint8 x)`` with a raw byte argument
of ``0xff000001`` and with ``0x00000001``. Both are fed to the contract and both will
look like the number ``1`` as far as ``x`` is concerned, but ``msg.data`` will
be different, so if you use ``sha3(msg.data)`` for anything, you will get different results.
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