Shamira Changeset - ccb4a27318f1

Changeset - ccb4a27318f1

Parent rev.

Child rev.

[Not reviewed]

default

0 1 1

Laman - 5 years ago 2019-05-29 11:37:14

added readme

2 files changed with 8 insertions and 0 deletions:

readme.md

src/shamira.py

0 comments (0 inline, 0 general)

readme.md

➞

Show inline comments

@@ new file 100644 @@
 # Shamira #
 Implements Shamir's secret sharing algorithm. Splits a string or a byte sequence byte-per-byte into n<255 shares, with any k of them sufficient for reconstruction of the original input.
 Outputs the shares as hexadecimal, Base32 or Base64 encoded strings.
 Can be used on its own from the command line by invoking shamira.py or as a library by importing shamira.py.

src/shamira.py

➞

Show inline comments

 # GNU GPLv3, see LICENSE
 import os
 import re
 import base64
 import binascii
 import gf256
 class SException(Exception): pass
 class InvalidParams(SException): pass
 class DetectionException(SException): pass
 class DecodingException(SException): pass
 class MalformedShare(SException): pass
 def _shareByte(secretB,k,n):
 	if not k<=n<255:
 		raise InvalidParams("Failed k<=n<255, k={0}, n={1}".format(k,n))
 	# we might be concerned with zero coefficients degenerating our polynomial, but there's no reason - we still need k shares to determine it is the case
 	coefs=[int(secretB)]+[int(b) for b in os.urandom(k-1)]
 	points=[gf256.evaluate(coefs,i) for i in range(1,n+1)]
 	return points
 def generateRaw(secret,k,n):
 	"""Splits secret into shares.
 	:param secret: (bytes)
 	:param k: number of shares necessary for secret recovery. 1 <= k <= n
 	:param n: (int) number of shares generated. 1 <= n < 255
 	:return: [(i, (bytes) share), ...]"""
 	shares=[_shareByte(b,k,n) for b in secret]
 	return [(i+1, bytes([s[i] for s in shares])) for i in range(n)]
 def reconstructRaw(*shares):
 	"""Tries to recover the secret from its shares.
 	:param shares: ((i, (bytes) share), ...)
 	:return: (bytes) reconstructed secret. Too few shares returns garbage."""
 	secretLen=len(shares[0][1])
 	res=[None]*secretLen
 	for i in range(secretLen):

0 comments (0 inline, 0 general)