Integrity checking

The PSKC format allows for message authentication and integrity checking for some of the values stored within the PSKC file.

Integrity checking is done transparently when accessing attributes that are encrypted and contain a ValueMAC.

Once the PSKC encryption key has been set up, key values can be explicitly checked using the check() method:

>>> pskc = PSKC('somefile.pskcxml')
>>> pskc.encryption.derive_key('qwerty')
>>> pskc.mac.algorithm
'http://www.w3.org/2000/09/xmldsig#hmac-sha1'
>>> all(key.check() for key in pskc.keys)
True

The MAC class

class pskc.mac.MAC

algorithm

The name of the MAC algorithm to use (currently HMAC-MD5, HMAC-SHA1, HMAC-SHA224, HMAC-SHA256, HMAC-SHA384 and HMAC-SHA512 are supported).

key

For HMAC checking, this contains the binary value of the MAC key. The MAC key is generated specifically for each PSKC file and encrypted with the PSKC encryption key, so the PSKC file should be decrypted first (see PSKC encryption).

setup(...)

Configure an encrypted MAC key.

Parameters:

• algorithm (str) – encryption algorithm
• key (binary) – the encryption key to use

None of the arguments are required. By default HMAC-SHA1 will be used as a MAC algorithm. If no key is configured a random key will be generated with the length of the output of the configured hash.