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86 lines
3.2 KiB
ReStructuredText
86 lines
3.2 KiB
ReStructuredText
:mod:`uhashlib` -- hashing algorithms
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=====================================
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.. module:: uhashlib
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:synopsis: hashing algorithms
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This module implements binary data hashing algorithms. The exact inventory
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of available algorithms depends on a board. Among the algorithms which may
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be implemented:
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* SHA256 - The current generation, modern hashing algorithm (of SHA2 series).
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It is suitable for cryptographically-secure purposes. Included in the
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MicroPython core and any board is recommended to provide this, unless
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it has particular code size constraints.
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* SHA1 - A previous generation algorithm. Not recommended for new usages,
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but SHA1 is a part of number of Internet standards and existing
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applications, so boards targetting network connectivity and
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interoperatiability will try to provide this.
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* MD5 - A legacy algorithm, not considered cryptographically secure. Only
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selected boards, targetting interoperatibility with legacy applications,
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will offer this.
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Constructors
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------------
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.. class:: uhashlib.sha256([data])
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Create an SHA256 hasher object and optionally feed ``data`` into it.
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.. class:: uhashlib.sha1([data])
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Create an SHA1 hasher object and optionally feed ``data`` into it.
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.. class:: uhashlib.md5([data])
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Create an MD5 hasher object and optionally feed ``data`` into it.
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.. only:: port_wipy
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.. class:: uhashlib.sha1([data[, block_size]])
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Create a sha1 hasher object and optionally feed ``data`` or ``data and block_size`` into it.
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.. class:: uhashlib.sha256([data[, block_size]])
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Create a sha256 hasher object and optionally feed ``data`` or ``data and block_size`` into it.
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.. admonition:: CPython extension
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:class: attention
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Due to hardware implementation details of the WiPy, data must be buffered before being
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digested, which would make it impossible to calculate the hash of big blocks of data that
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do not fit in RAM. In this case, since most likely the total size of the data is known
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in advance, the size can be passed to the constructor and hence the HASH hardware engine
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of the WiPy can be properly initialized without needing buffering. If ``block_size`` is
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to be given, an initial chunk of ``data`` must be passed as well. **When using this extension,
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care must be taken to make sure that the length of all intermediate chunks (including the
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initial one) is a multiple of 4 bytes.** The last chunk may be of any length.
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Example::
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hash = uhashlib.sha1('abcd1234', 1001) # length of the initial piece is multiple of 4 bytes
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hash.update('1234') # also multiple of 4 bytes
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...
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hash.update('12345') # last chunk may be of any length
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hash.digest()
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Methods
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-------
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.. method:: hash.update(data)
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Feed more binary data into hash.
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.. method:: hash.digest()
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Return hash for all data passed through hash, as a bytes object. After this
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method is called, more data cannot be fed into the hash any longer.
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.. method:: hash.hexdigest()
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This method is NOT implemented. Use ``ubinascii.hexlify(hash.digest())``
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to achieve a similar effect.
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