Added in version 3.6.
Source code:
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The secrets module is used for generating cryptographically strong random numbers suitable for managing data such as passwords, account authentication, security tokens, and related secrets.
In particular, secrets should be used in preference to the default pseudo-random number generator in the
module, which is designed for modelling and simulation, not security or cryptography.
Random numbers
The secrets module provides access to the most secure source of randomness that your operating system provides.
classsecrets.SystemRandom
A class for generating random numbers using the highest-quality sources provided by the operating system. See
for additional details.
secrets.choice(seq)
Return a randomly chosen element from a non-empty sequence.
secrets.randbelow(exclusive_upper_bound)
Return a random int in the range [0, exclusive_upper_bound).
secrets.randbits(k)
Return a non-negative int with k random bits.
Generating tokens
The secrets module provides functions for generating secure tokens, suitable for applications such as password resets, hard-to-guess URLs, and similar.
secrets.token_bytes(nbytes=None)
Return a random byte string containing nbytes number of bytes.
If nbytes is not specified or None,
is used instead.
>>> token_bytes(16)b'\xebr\x17D*t\xae\xd4\xe3S\xb6\xe2\xebP1\x8b'secrets.token_hex(nbytes=None)
Return a random text string, in hexadecimal. The string has nbytes random bytes, each byte converted to two hex digits.
If nbytes is not specified or None,
is used instead.
>>> token_hex(16)'f9bf78b9a18ce6d46a0cd2b0b86df9da'secrets.token_urlsafe(nbytes=None)
Return a random URL-safe text string, containing nbytes random bytes. The text is Base64 encoded, so on average each byte results in approximately 1.3 characters.
If nbytes is not specified or None,
is used instead.
>>> token_urlsafe(16)'Drmhze6EPcv0fN_81Bj-nA'How many bytes should tokens use?
To be secure against
, tokens need to have sufficient randomness. Unfortunately, what is considered sufficient will necessarily increase as computers get more powerful and able to make more guesses in a shorter period. As of 2015, it is believed that 32 bytes (256 bits) of randomness is sufficient for the typical use-case expected for the secrets module.
For those who want to manage their own token length, you can explicitly specify how much randomness is used for tokens by giving an
argument to the various token_* functions. That argument is taken as the number of bytes of randomness to use.
Otherwise, if no argument is provided, or if the argument is None, the token_* functions use
instead.
secrets.DEFAULT_ENTROPY
Default number of bytes of randomness used by the token_* functions.
The exact value is subject to change at any time, including during maintenance releases.
Other functions
secrets.compare_digest(a, b)
Return True if strings or
a and b are equal, otherwise False, using a “constant-time compare” to reduce the risk of
. See
for additional details.
Recipes and best practices
This section shows recipes and best practices for using secrets to manage a basic level of security.
Generate an eight-character alphanumeric password:
importstringimportsecretsalphabet=string.ascii_letters+string.digitspassword=''.join(secrets.choice(alphabet)foriinrange(8))Note
Applications should not
store passwords in a recoverable format
, whether plain text or encrypted. They should be salted and hashed using a cryptographically strong one-way (irreversible) hash function.
Generate a ten-character alphanumeric password with at least one lowercase character, at least one uppercase character, and at least three digits:
importstringimportsecretsalphabet=string.ascii_letters+string.digitswhileTrue:password=''.join(secrets.choice(alphabet)foriinrange(10))if(any(c.islower()forcinpassword)andany(c.isupper()forcinpassword)andsum(c.isdigit()forcinpassword)>=3):breakGenerate an
:
importsecrets# On standard Linux systems, use a convenient dictionary file.# Other platforms may need to provide their own word-list.withopen('/usr/share/dict/words')asf:words=[word.strip()forwordinf]password=' '.join(secrets.choice(words)foriinrange(4))Generate a hard-to-guess temporary URL containing a security token suitable for password recovery applications:
importsecretsurl='https://example.com/reset='+secrets.token_urlsafe()