Skip to main content
Python Software Foundation 20th Year Anniversary Fundraiser  Donate today!

No project description provided

Project description


Fast, secure, pure python implementation of Shamir's secret sharing algorithm.

why to use it

Shamir's secret sharing is useful for providing an "N of M" layer.
For example, password recovery security questions could be cryptographically
imeplemented with this algorithm. Security question answers are
put through a key-derivation-function (KDF) or hash and each one is used to
encrypt a different secret. Then, the answer to any say 5 of 11 security
questions would be enouch to recover the secret.

how to use it

.. code-block:: python
secret, shares = make_random_secret(3, 5)
# generate shares such that 3 of 5 can recover the secret
secret = recover_secret(shares)

Shamir's secret sharing algorithm operates on integer X, Y points,
and the secret it stores is a random integer. To be useful, it must be
combined with other algorithms. Here's a high level example:

.. code-block:: python
# encrypt, decrypt, hash, and kdf are external functions

def two_of_three_encrypt(plaintext, pw0, pw1, pw2):
'given a plaintext, secure it so that any 2 may access in the future'
secret, shares = shamir.make_random_shares(2, 3)
def encrypt_share(share, pw):
return encrypt(key=kdf(pw), plaintext=repr(share))
return (
encrypt(key=hash(hex(secret)), plaintext=plaintext)) + tuple(
[encrypt(key=kef(pw), plaintext=repr(share))
for pw, share in zip((pw0, pw1, pw2), shares)])

def two_of_three_decrypt(encrypted, pwA, pwB):
'recover the plaintext given 2 of the 3 passwords used to secure'
ciphertext, shares = encrypted[0], encrypted[1:]
keyA, keyB = kdf(pwA), kdf(pwB)
decrypted_shares = []
for share in shares:
for key in (keyA, keyB):
decrypt(key=keyA, ciphertext=share))
except Exception:
if len(decrypted_shares) < 2:
raise ValueError('bad password')
return decrypt(

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for shamir, version 17.12.0
Filename, size File type Python version Upload date Hashes
Filename, size shamir-17.12.0-py2.py3-none-any.whl (5.2 kB) File type Wheel Python version py2.py3 Upload date Hashes View
Filename, size shamir-17.12.0.tar.gz (3.4 kB) File type Source Python version None Upload date Hashes View

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring DigiCert DigiCert EV certificate Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page