15.2 md5 -- MD5 message digest algorithm
Keywords: lib

# 15.2 `md5` -- MD5 message digest algorithm

This module implements the interface to RSA's MD5 message digest algorithm (see also Internet RFC 1321). Its use is quite straightforward: use `new()` to create an md5 object. You can now feed this object with arbitrary strings using the `update()` method, and at any point you can ask it for the digest (a strong kind of 128-bit checksum, a.k.a. ``fingerprint'') of the concatenation of the strings fed to it so far using the `digest()` method.

For example, to obtain the digest of the string `'Nobody inspects the spammish repetition'`:

      >>> import md5
      >>> m = md5.new()
      >>> m.update("Nobody inspects")
      >>> m.update(" the spammish repetition")
      >>> m.digest()
      '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'

More condensed:

      >>> md5.new("Nobody inspects the spammish repetition").digest()
      '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'

The following values are provided as constants in the module and as attributes of the md5 objects returned by `new()`:

`digest_size`
  The size of the resulting digest in bytes. This is always `16`.

md5 objects support the following methods:

`new`([arg])
  Return a new md5 object. If arg is present, the method call `update(arg)` is made.

`md5`([arg])
  For backward compatibility reasons, this is an alternative name for the `new()` function.

An md5 object has the following methods:

`update`(arg)
  Update the md5 object with the string arg. Repeated calls are equivalent to a single call with the concatenation of all the arguments: `m.update(a); m.update(b)` is equivalent to `m.update(a+b)`.

`digest`()
  Return the digest of the strings passed to the `update()` method so far. This is a 16-byte string which may contain non-ASCII characters, including null bytes.

`hexdigest`()
  Like `digest()` except the digest is returned as a string of length 32, containing only hexadecimal digits. This may be used to exchange the value safely in email or other non-binary environments.

`copy`()
  Return a copy (``clone'') of the md5 object. This can be used to efficiently compute the digests of strings that share a common initial substring.

See Also:

Module `sha`:
  Similar module implementing the Secure Hash Algorithm (SHA). The SHA algorithm is considered a more secure hash.