Package Crypto :: Package Protocol :: Module KDF
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Module KDF

This file contains a collection of standard key derivation functions.

A key derivation function derives one or more secondary secret keys from one primary secret (a master key or a pass phrase).

This is typically done to insulate the secondary keys from each other, to avoid that leakage of a secondary key compromises the security of the master key, or to thwart attacks on pass phrases (e.g. via rainbow tables).

Functions
 
PBKDF1(password, salt, dkLen, count=1000, hashAlgo=None)
Derive one key from a password (or passphrase).
 
PBKDF2(password, salt, dkLen=16, count=1000, prf=None)
Derive one or more keys from a password (or passphrase).
Variables
  __package__ = 'Crypto.Protocol'
Function Details

PBKDF1(password, salt, dkLen, count=1000, hashAlgo=None)

 

Derive one key from a password (or passphrase).

This function performs key derivation according an old version of the PKCS#5 standard (v1.5).

This algorithm is called PBKDF1. Even though it is still described in the latest version of the PKCS#5 standard (version 2, or RFC2898), newer applications should use the more secure and versatile PBKDF2 instead.

Parameters:
  • password (string) - The secret password or pass phrase to generate the key from.
  • salt (byte string) - An 8 byte string to use for better protection from dictionary attacks. This value does not need to be kept secret, but it should be randomly chosen for each derivation.
  • dkLen (integer) - The length of the desired key. Default is 16 bytes, suitable for instance for Crypto.Cipher.AES.
  • count (integer) - The number of iterations to carry out. It's recommended to use at least 1000.
  • hashAlgo (module) - The hash algorithm to use, as a module or an object from the Crypto.Hash package. The digest length must be no shorter than dkLen. The default algorithm is SHA1.
Returns:
A byte string of length dkLen that can be used as key.

PBKDF2(password, salt, dkLen=16, count=1000, prf=None)

 

Derive one or more keys from a password (or passphrase).

This performs key derivation according to the PKCS#5 standard (v2.0), by means of the PBKDF2 algorithm.

Parameters:
  • password (string) - The secret password or pass phrase to generate the key from.
  • salt (string) - A string to use for better protection from dictionary attacks. This value does not need to be kept secret, but it should be randomly chosen for each derivation. It is recommended to be at least 8 bytes long.
  • dkLen (integer) - The cumulative length of the desired keys. Default is 16 bytes, suitable for instance for Crypto.Cipher.AES.
  • count (integer) - The number of iterations to carry out. It's recommended to use at least 1000.
  • prf (callable) - A pseudorandom function. It must be a function that returns a pseudorandom string from two parameters: a secret and a salt. If not specified, HMAC-SHA1 is used.
Returns:
A byte string of length dkLen that can be used as key material. If you wanted multiple keys, just break up this string into segments of the desired length.