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354 lines
11 KiB
Python
354 lines
11 KiB
Python
#! /usr/bin/pythonw
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# The Keccak sponge function, designed by Guido Bertoni, Joan Daemen,
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# questions, please refer to our website: http://keccak.noekeon.org/
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#
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# Implementation by Renaud Bauvin,
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# hereby denoted as "the implementer".
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#
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# To the extent possible under law, the implementer has waived all copyright
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# and related or neighboring rights to the source code in this file.
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# http://creativecommons.org/publicdomain/zero/1.0/
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import math
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class KeccakError(Exception):
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"""Class of error used in the Keccak implementation
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Use: raise KeccakError.KeccakError("Text to be displayed")"""
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def __init__(self, value):
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self.value = value
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def __str__(self):
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return repr(self.value)
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class Keccak:
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"""
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Class implementing the Keccak sponge function
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"""
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def __init__(self, b=1600):
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"""Constructor:
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b: parameter b, must be 25, 50, 100, 200, 400, 800 or 1600 (default value)"""
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self.setB(b)
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def setB(self,b):
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"""Set the value of the parameter b (and thus w,l and nr)
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b: parameter b, must be choosen among [25, 50, 100, 200, 400, 800, 1600]
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"""
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if b not in [25, 50, 100, 200, 400, 800, 1600]:
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raise KeccakError.KeccakError('b value not supported - use 25, 50, 100, 200, 400, 800 or 1600')
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# Update all the parameters based on the used value of b
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self.b=b
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self.w=b//25
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self.l=int(math.log(self.w,2))
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self.nr=12+2*self.l
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# Constants
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## Round constants
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RC=[0x0000000000000001,
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0x0000000000008082,
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0x800000000000808A,
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0x8000000080008000,
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0x000000000000808B,
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0x0000000080000001,
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0x8000000080008081,
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0x8000000000008009,
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0x000000000000008A,
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0x0000000000000088,
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0x0000000080008009,
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0x000000008000000A,
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0x000000008000808B,
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0x800000000000008B,
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0x8000000000008089,
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0x8000000000008003,
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0x8000000000008002,
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0x8000000000000080,
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0x000000000000800A,
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0x800000008000000A,
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0x8000000080008081,
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0x8000000000008080,
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0x0000000080000001,
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0x8000000080008008]
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## Rotation offsets
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r=[[0, 36, 3, 41, 18] ,
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[1, 44, 10, 45, 2] ,
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[62, 6, 43, 15, 61] ,
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[28, 55, 25, 21, 56] ,
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[27, 20, 39, 8, 14] ]
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## Generic utility functions
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def rot(self,x,n):
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"""Bitwise rotation (to the left) of n bits considering the \
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string of bits is w bits long"""
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n = n%self.w
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return ((x>>(self.w-n))+(x<<n))%(1<<self.w)
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def fromHexStringToLane(self, string):
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"""Convert a string of bytes written in hexadecimal to a lane value"""
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#Check that the string has an even number of characters i.e. whole number of bytes
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if len(string)%2!=0:
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raise KeccakError.KeccakError("The provided string does not end with a full byte")
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#Perform the modification
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temp=''
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nrBytes=len(string)//2
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for i in range(nrBytes):
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offset=(nrBytes-i-1)*2
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temp+=string[offset:offset+2]
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return int(temp, 16)
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def fromLaneToHexString(self, lane):
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"""Convert a lane value to a string of bytes written in hexadecimal"""
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laneHexBE = (("%%0%dX" % (self.w//4)) % lane)
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#Perform the modification
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temp=''
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nrBytes=len(laneHexBE)//2
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for i in range(nrBytes):
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offset=(nrBytes-i-1)*2
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temp+=laneHexBE[offset:offset+2]
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return temp.upper()
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def printState(self, state, info):
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"""Print on screen the state of the sponge function preceded by \
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string info
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state: state of the sponge function
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info: a string of characters used as identifier"""
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print("Current value of state: %s" % (info))
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for y in range(5):
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line=[]
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for x in range(5):
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line.append(hex(state[x][y]))
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print('\t%s' % line)
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### Conversion functions String <-> Table (and vice-versa)
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def convertStrToTable(self,string):
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"""Convert a string of bytes to its 5x5 matrix representation
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string: string of bytes of hex-coded bytes (e.g. '9A2C...')"""
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#Check that input paramaters
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if self.w%8!= 0:
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raise KeccakError("w is not a multiple of 8")
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if len(string)!=2*(self.b)//8:
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raise KeccakError.KeccakError("string can't be divided in 25 blocks of w bits\
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i.e. string must have exactly b bits")
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#Convert
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output=[[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0]]
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for x in range(5):
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for y in range(5):
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offset=2*((5*y+x)*self.w)//8
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output[x][y]=self.fromHexStringToLane(string[offset:offset+(2*self.w//8)])
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return output
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def convertTableToStr(self,table):
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"""convert 5x5 matrix to string"""
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#Check input format
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if self.w%8!= 0:
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raise KeccakError.KeccakError("w is not a multiple of 8")
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if (len(table)!=5) or (False in [len(row)==5 for row in table]):
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raise KeccakError.KeccakError("table must be 5x5")
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#Convert
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output=['']*25
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for x in range(5):
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for y in range(5):
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output[5*y+x]=self.fromLaneToHexString(table[x][y])
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output =''.join(output).upper()
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return output
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def Round(self,A,RCfixed):
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"""Perform one round of computation as defined in the Keccak-f permutation
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A: current state (5x5 matrix)
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RCfixed: value of round constant to use (integer)
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"""
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#Initialisation of temporary variables
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B=[[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0]]
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C= [0,0,0,0,0]
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D= [0,0,0,0,0]
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#Theta step
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for x in range(5):
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C[x] = A[x][0]^A[x][1]^A[x][2]^A[x][3]^A[x][4]
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for x in range(5):
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D[x] = C[(x-1)%5]^self.rot(C[(x+1)%5],1)
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for x in range(5):
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for y in range(5):
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A[x][y] = A[x][y]^D[x]
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#Rho and Pi steps
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for x in range(5):
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for y in range(5):
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B[y][(2*x+3*y)%5] = self.rot(A[x][y], self.r[x][y])
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#Chi step
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for x in range(5):
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for y in range(5):
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A[x][y] = B[x][y]^((~B[(x+1)%5][y]) & B[(x+2)%5][y])
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#Iota step
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A[0][0] = A[0][0]^RCfixed
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return A
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def KeccakF(self,A, verbose=False):
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"""Perform Keccak-f function on the state A
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A: 5x5 matrix containing the state
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verbose: a boolean flag activating the printing of intermediate computations
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"""
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if verbose:
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self.printState(A,"Before first round")
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for i in range(self.nr):
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#NB: result is truncated to lane size
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A = self.Round(A,self.RC[i]%(1<<self.w))
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if verbose:
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self.printState(A,"Satus end of round #%d/%d" % (i+1,self.nr))
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return A
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### Padding rule
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def pad10star1(self, M, n):
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"""Pad M with the pad10*1 padding rule to reach a length multiple of r bits
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M: message pair (length in bits, string of hex characters ('9AFC...')
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n: length in bits (must be a multiple of 8)
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Example: pad10star1([60, 'BA594E0FB9EBBD30'],8) returns 'BA594E0FB9EBBD93'
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"""
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[my_string_length, my_string]=M
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# Check the parameter n
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if n%8!=0:
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raise KeccakError.KeccakError("n must be a multiple of 8")
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# Check the length of the provided string
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if len(my_string)%2!=0:
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#Pad with one '0' to reach correct length (don't know test
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#vectors coding)
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my_string=my_string+'0'
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if my_string_length>(len(my_string)//2*8):
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raise KeccakError.KeccakError("the string is too short to contain the number of bits announced")
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nr_bytes_filled=my_string_length//8
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nbr_bits_filled=my_string_length%8
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l = my_string_length % n
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if ((n-8) <= l <= (n-2)):
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if (nbr_bits_filled == 0):
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my_byte = 0
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else:
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my_byte=int(my_string[nr_bytes_filled*2:nr_bytes_filled*2+2],16)
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my_byte=(my_byte>>(8-nbr_bits_filled))
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my_byte=my_byte+2**(nbr_bits_filled)+2**7
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my_byte="%02X" % my_byte
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my_string=my_string[0:nr_bytes_filled*2]+my_byte
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else:
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if (nbr_bits_filled == 0):
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my_byte = 0
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else:
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my_byte=int(my_string[nr_bytes_filled*2:nr_bytes_filled*2+2],16)
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my_byte=(my_byte>>(8-nbr_bits_filled))
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my_byte=my_byte+2**(nbr_bits_filled)
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my_byte="%02X" % my_byte
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my_string=my_string[0:nr_bytes_filled*2]+my_byte
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while((8*len(my_string)//2)%n < (n-8)):
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my_string=my_string+'00'
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my_string = my_string+'80'
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return my_string
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def Keccak(self,M,r=1024,c=576,n=1024,verbose=False):
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"""Compute the Keccak[r,c,d] sponge function on message M
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M: message pair (length in bits, string of hex characters ('9AFC...')
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r: bitrate in bits (defautl: 1024)
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c: capacity in bits (default: 576)
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n: length of output in bits (default: 1024),
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verbose: print the details of computations(default:False)
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"""
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#Check the inputs
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if (r<0) or (r%8!=0):
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raise KeccakError.KeccakError('r must be a multiple of 8 in this implementation')
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if (n%8!=0):
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raise KeccakError.KeccakError('outputLength must be a multiple of 8')
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self.setB(r+c)
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if verbose:
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print("Create a Keccak function with (r=%d, c=%d (i.e. w=%d))" % (r,c,(r+c)//25))
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#Compute lane length (in bits)
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w=(r+c)//25
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# Initialisation of state
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S=[[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0],
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[0,0,0,0,0]]
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#Padding of messages
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P = self.pad10star1(M, r)
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if verbose:
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print("String ready to be absorbed: %s (will be completed by %d x '00')" % (P, c//8))
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#Absorbing phase
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for i in range((len(P)*8//2)//r):
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Pi=self.convertStrToTable(P[i*(2*r//8):(i+1)*(2*r//8)]+'00'*(c//8))
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for y in range(5):
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for x in range(5):
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S[x][y] = S[x][y]^Pi[x][y]
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S = self.KeccakF(S, verbose)
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if verbose:
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print("Value after absorption : %s" % (self.convertTableToStr(S)))
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#Squeezing phase
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Z = ''
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outputLength = n
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while outputLength>0:
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string=self.convertTableToStr(S)
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Z = Z + string[:r*2//8]
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outputLength -= r
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if outputLength>0:
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S = self.KeccakF(S, verbose)
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# NB: done by block of length r, could have to be cut if outputLength
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# is not a multiple of r
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if verbose:
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print("Value after squeezing : %s" % (self.convertTableToStr(S)))
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return Z[:2*n//8]
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