#!/usr/local/bin/python # $RCSfile: SERPREF.PY,v $ # $Id: SERPREF.PY,v 1.15 1998/03/05 16:46:27 fms Exp fms $ # written by Frank Stajano, http://www.cl.cam.ac.uk/~fms27/ # Cambridge University Computer Laboratory # Development started on 1998 02 12 # # Serpent cipher invented by Eli Biham, Ross Anderson, Lars Knudsen. # -------------------------------------------------------------- """This is a reference implementation of the Serpent cipher invented by Eli Biham, Ross Anderson, Lars Knudsen. It is written for the human reader more than for the machine and, as such, it is optimised for clarity rather than speed. ("Premature optimisation is the root of all evil.") It can print out all the intermediate results (such as the subkeys) for a given input and key so that implementers debugging erroneous code can quickly verify which one of the building blocks is giving the wrong answers.""" # -------------------------------------------------------------- # Requires python 1.5, freely available from http://www.python.org/ # -------------------------------------------------------------- import string import sys import getopt import re import whrandom # -------------------------------------------------------------- # Functions used in the formal description of the cipher def S(box, input): """Apply S-box number 'box' to 4-bit bitstring 'input' and return a 4-bit bitstring as the result.""" return SBoxBitstring[box][input] def SInverse(box, output): """Apply S-box number 'box' in reverse to 4-bit bitstring 'output' and return a 4-bit bitstring (the input) as the result.""" return SBoxBitstringInverse[box][output] def SHat(box, input): """Apply a parallel array of 32 copies of S-box number 'box' to the 128-bit bitstring 'input' and return a 128-bit bitstring as the result.""" result = "" for i in range(32): result = result + S(box, input[4*i:4*(i+1)]) return result def SHatInverse(box, output): """Apply, in reverse, a parallel array of 32 copies of S-box number 'box' to the 128-bit bitstring 'output' and return a 128-bit bitstring (the input) as the result.""" result = "" for i in range(32): result = result + SInverse(box, output[4*i:4*(i+1)]) return result def SBitslice(box, words): """Take 'words', a list of 4 32-bit bitstrings, least significant word first. Return a similar list of 4 32-bit bitstrings obtained as follows. For each bit position from 0 to 31, apply S-box number 'box' to the 4 input bits coming from the current position in each of the items in 'words'; and put the 4 output bits in the corresponding positions in the output words.""" result = ["", "", "", ""] for i in range(32): # ideally in parallel quad = S(box, words[0][i] + words[1][i] + words[2][i] + words[3][i]) for j in range(4): result[j] = result[j] + quad[j] return result def SBitsliceInverse(box, words): """Take 'words', a list of 4 32-bit bitstrings, least significant word first. Return a similar list of 4 32-bit bitstrings obtained as follows. For each bit position from 0 to 31, apply S-box number 'box' in reverse to the 4 output bits coming from the current position in each of the items in the supplied 'words'; and put the 4 input bits in the corresponding positions in the returned words.""" result = ["", "", "", ""] for i in range(32): # ideally in parallel quad = SInverse( box, words[0][i] + words[1][i] + words[2][i] + words[3][i]) for j in range(4): result[j] = result[j] + quad[j] return result def LT(input): """Apply the table-based version of the linear transformation to the 128-bit string 'input' and return a 128-bit string as the result.""" if len(input) != 128: raise ValueError, "input to LT is not 128 bit long" result = "" for i in range(len(LTTable)): outputBit = "0" for j in LTTable[i]: outputBit = xor(outputBit, input[j]) result = result + outputBit return result def LTInverse(output): """Apply the table-based version of the inverse of the linear transformation to the 128-bit string 'output' and return a 128-bit string (the input) as the result.""" if len(output) != 128: raise ValueError, "input to inverse LT is not 128 bit long" result = "" for i in range(len(LTTableInverse)): inputBit = "0" for j in LTTableInverse[i]: inputBit = xor(inputBit, output[j]) result = result + inputBit return result def LTBitslice(X): """Apply the equations-based version of the linear transformation to 'X', a list of 4 32-bit bitstrings, least significant bitstring first, and return another list of 4 32-bit bitstrings as the result.""" X[0] = rotateLeft(X[0], 13) X[2] = rotateLeft(X[2], 3) X[1] = xor(X[1], X[0], X[2]) X[3] = xor(X[3], X[2], shiftLeft(X[0], 3)) X[1] = rotateLeft(X[1], 1) X[3] = rotateLeft(X[3], 7) X[0] = xor(X[0], X[1], X[3]) X[2] = xor(X[2], X[3], shiftLeft(X[1], 7)) X[0] = rotateLeft(X[0], 5) X[2] = rotateLeft(X[2], 22) return X def LTBitsliceInverse(X): """Apply, in reverse, the equations-based version of the linear transformation to 'X', a list of 4 32-bit bitstrings, least significant bitstring first, and return another list of 4 32-bit bitstrings as the result.""" X[2] = rotateRight(X[2], 22) X[0] = rotateRight(X[0], 5) X[2] = xor(X[2], X[3], shiftLeft(X[1], 7)) X[0] = xor(X[0], X[1], X[3]) X[3] = rotateRight(X[3], 7) X[1] = rotateRight(X[1], 1) X[3] = xor(X[3], X[2], shiftLeft(X[0], 3)) X[1] = xor(X[1], X[0], X[2]) X[2] = rotateRight(X[2], 3) X[0] = rotateRight(X[0], 13) return X def IP(input): """Apply the Initial Permutation to the 128-bit bitstring 'input' and return a 128-bit bitstring as the result.""" return applyPermutation(IPTable, input) def FP(input): """Apply the Final Permutation to the 128-bit bitstring 'input' and return a 128-bit bitstring as the result.""" return applyPermutation(FPTable, input) def IPInverse(output): """Apply the Initial Permutation in reverse.""" return FP(output) def FPInverse(output): """Apply the Final Permutation in reverse.""" return IP(output) def applyPermutation(permutationTable, input): """Apply the permutation specified by the 128-element list 'permutationTable' to the 128-bit bitstring 'input' and return a 128-bit bitstring as the result.""" if len(input) != len(permutationTable): raise ValueError, "input size (%d) does not match perm table size (%d)"\ % (len(input), len(permutationTable)) result = "" for i in range(len(permutationTable)): result = result + input[permutationTable[i]] return result def R(i, BHati, KHat): """Apply round 'i' to the 128-bit bitstring 'BHati', returning another 128-bit bitstring (conceptually BHatiPlus1). Do this using the appropriately numbered subkey(s) from the 'KHat' list of 33 128-bit bitstrings.""" O.show("BHati", BHati, "(i=%2d) BHati" % i) xored = xor(BHati, KHat[i]) O.show("xored", xored, "(i=%2d) xored" % i) SHati = SHat(i, xored) O.show("SHati", SHati, "(i=%2d) SHati" % i) if 0 <= i <= r-2: BHatiPlus1 = LT(SHati) elif i == r-1: BHatiPlus1 = xor(SHati, KHat[r]) else: raise ValueError, "round %d is out of 0..%d range" % (i, r-1) O.show("BHatiPlus1", BHatiPlus1, "(i=%2d) BHatiPlus1" % i) return BHatiPlus1 def RInverse(i, BHatiPlus1, KHat): """Apply round 'i' in reverse to the 128-bit bitstring 'BHatiPlus1', returning another 128-bit bitstring (conceptually BHati). Do this using the appropriately numbered subkey(s) from the 'KHat' list of 33 128-bit bitstrings.""" O.show("BHatiPlus1", BHatiPlus1, "(i=%2d) BHatiPlus1" % i) if 0 <= i <= r-2: SHati = LTInverse(BHatiPlus1) elif i == r-1: SHati = xor(BHatiPlus1, KHat[r]) else: raise ValueError, "round %d is out of 0..%d range" % (i, r-1) O.show("SHati", SHati, "(i=%2d) SHati" % i) xored = SHatInverse(i, SHati) O.show("xored", xored, "(i=%2d) xored" % i) BHati = xor(xored, KHat[i]) O.show("BHati", BHati, "(i=%2d) BHati" % i) return BHati def RBitslice(i, Bi, K): """Apply round 'i' (bitslice version) to the 128-bit bitstring 'Bi' and return another 128-bit bitstring (conceptually B i+1). Use the appropriately numbered subkey(s) from the 'K' list of 33 128-bit bitstrings.""" O.show("Bi", Bi, "(i=%2d) Bi" % i) # 1. Key mixing xored = xor (Bi, K[i]) O.show("xored", xored, "(i=%2d) xored" % i) # 2. S Boxes Si = SBitslice(i, quadSplit(xored)) # Input and output to SBitslice are both lists of 4 32-bit bitstrings O.show("Si", Si, "(i=%2d) Si" % i, "tlb") # 3. Linear Transformation if i == r-1: # In the last round, replaced by an additional key mixing BiPlus1 = xor(quadJoin(Si), K[r]) else: BiPlus1 = quadJoin(LTBitslice(Si)) # BIPlus1 is a 128-bit bitstring O.show("BiPlus1", BiPlus1, "(i=%2d) BiPlus1" % i) return BiPlus1 def RBitsliceInverse(i, BiPlus1, K): """Apply the inverse of round 'i' (bitslice version) to the 128-bit bitstring 'BiPlus1' and return another 128-bit bitstring (conceptually B i). Use the appropriately numbered subkey(s) from the 'K' list of 33 128-bit bitstrings.""" O.show("BiPlus1", BiPlus1, "(i=%2d) BiPlus1" % i) # 3. Linear Transformation if i == r-1: # In the last round, replaced by an additional key mixing Si = quadSplit(xor(BiPlus1, K[r])) else: Si = LTBitsliceInverse(quadSplit(BiPlus1)) # SOutput (same as LTInput) is a list of 4 32-bit bitstrings O.show("Si", Si, "(i=%2d) Si" % i, "tlb") # 2. S Boxes xored = SBitsliceInverse(i, Si) # SInput and SOutput are both lists of 4 32-bit bitstrings O.show("xored", xored, "(i=%2d) xored" % i) # 1. Key mixing Bi = xor (quadJoin(xored), K[i]) O.show("Bi", Bi, "(i=%2d) Bi" % i) return Bi def encrypt(plainText, userKey): """Encrypt the 128-bit bitstring 'plainText' with the 256-bit bitstring 'userKey', using the normal algorithm, and return a 128-bit ciphertext bitstring.""" O.show("fnTitle", "encrypt", None, "tu") O.show("plainText", plainText, "plainText") O.show("userKey", userKey, "userKey") K, KHat = makeSubkeys(userKey) BHat = IP(plainText) # BHat_0 at this stage for i in range(r): BHat = R(i, BHat, KHat) # Produce BHat_i+1 from BHat_i # BHat is now _32 i.e. _r C = FP(BHat) O.show("cipherText", C, "cipherText") return C def encryptBitslice(plainText, userKey): """Encrypt the 128-bit bitstring 'plainText' with the 256-bit bitstring 'userKey', using the bitslice algorithm, and return a 128-bit ciphertext bitstring.""" O.show("fnTitle", "encryptBitslice", None, "tu") O.show("plainText", plainText, "plainText") O.show("userKey", userKey, "userKey") K, KHat = makeSubkeys(userKey) B = plainText # B_0 at this stage for i in range(r): B = RBitslice(i, B, K) # Produce B_i+1 from B_i # B is now _r O.show("cipherText", B, "cipherText") return B def decrypt(cipherText, userKey): """Decrypt the 128-bit bitstring 'cipherText' with the 256-bit bitstring 'userKey', using the normal algorithm, and return a 128-bit plaintext bitstring.""" O.show("fnTitle", "decrypt", None, "tu") O.show("cipherText", cipherText, "cipherText") O.show("userKey", userKey, "userKey") K, KHat = makeSubkeys(userKey) BHat = FPInverse(cipherText) # BHat_r at this stage for i in range(r-1, -1, -1): # from r-1 down to 0 included BHat = RInverse(i, BHat, KHat) # Produce BHat_i from BHat_i+1 # BHat is now _0 plainText = IPInverse(BHat) O.show("plainText", plainText, "plainText") return plainText def decryptBitslice(cipherText, userKey): """Decrypt the 128-bit bitstring 'cipherText' with the 256-bit bitstring 'userKey', using the bitslice algorithm, and return a 128-bit plaintext bitstring.""" O.show("fnTitle", "decryptBitslice", None, "tu") O.show("cipherText", cipherText, "cipherText") O.show("userKey", userKey, "userKey") K, KHat = makeSubkeys(userKey) B = cipherText # B_r at this stage for i in range(r-1, -1, -1): # from r-1 down to 0 included B = RBitsliceInverse(i, B, K) # Produce B_i from B_i+1 # B is now _0 O.show("plainText", B, "plainText") return B def makeSubkeys(userKey): """Given the 256-bit bitstring 'userKey' (shown as K in the paper, but we can't use that name because of a collision with K[i] used later for something else), return two lists (conceptually K and KHat) of 33 128-bit bitstrings each.""" # Because in Python I can't index a list from anything other than 0, # I use a dictionary instead to legibly represent the w_i that are # indexed from -8. # We write the key as 8 32-bit words w-8 ... w-1 # ENOTE: w-8 is the least significant word w = {} for i in range(-8, 0): w[i] = userKey[(i+8)*32:(i+9)*32] O.show("wi", w[i], "(i=%2d) wi" % i) # We expand these to a prekey w0 ... w131 with the affine recurrence for i in range(132): w[i] = rotateLeft( xor(w[i-8], w[i-5], w[i-3], w[i-1], bitstring(phi, 32), bitstring(i,32)), 11) O.show("wi", w[i], "(i=%2d) wi" % i) # The round keys are now calculated from the prekeys using the S-boxes # in bitslice mode. Each k[i] is a 32-bit bitstring. k = {} for i in range(r+1): whichS = (r + 3 - i) % r k[0+i] = "" k[33+i] = "" k[66+i] = "" k[99+i] = "" for j in range(32): # for every bit in the k and w words # ENOTE: w0 and k0 are the least significant words, w99 and k99 # the most. input = w[0+i][j] + w[33+i][j] + w[66+i][j] + w[99+i][j] output = S(whichS, input) k[0+i] = k[0+i] + output[0] k[33+i] = k[33+i] + output[1] k[66+i] = k[66+i] + output[2] k[99+i] = k[99+i] + output[3] # We then renumber the 32 bit values k_j as 128 bit subkeys K_i. K = [] for i in range(33): # ENOTE: k4i is the least significant word, k4i+3 the most. K.append(k[4*i] + k[4*i+1] + k[4*i+2] + k[4*i+3]) # We now apply IP to the round key in order to place the key bits in # the correct column KHat = [] for i in range(33): KHat.append(IP(K[i])) O.show("Ki", K[i], "(i=%2d) Ki" % i) O.show("KHati", KHat[i], "(i=%2d) KHati" % i) return K, KHat # -------------------------------------------------------------- # Generic bit-level primitives # We represent the numbers manipulated by the cipher in a format that we # call 'bitstring'. This is a string of "0" and "1" characters containing # the binary representation of the number in little-endian format (so that # subscripting with an index of i gives bit number i, corresponding to a # weight of 2^i). This representation is only defined for nonnegative # numbers (you can see why: think of the great unnecessary mess that would # result from sign extension, two's complement and so on). Example: 10 # decimal is "0101" in bitstring format. def bitstring(n, minlen=1): """Translate n from integer to bitstring, padding it with 0s as necessary to reach the minimum length 'minlen'. 'n' must be >= 0 since the bitstring format is undefined for negative integers. Note that, while the bitstring format can represent arbitrarily large numbers, this is not so for Python's normal integer type: on a 32-bit machine, values of n >= 2^31 need to be expressed as python long integers or they will "look" negative and won't work. E.g. 0x80000000 needs to be passed in as 0x80000000L, or it will be taken as -2147483648 instead of +2147483648L. EXAMPLE: bitstring(10, 8) -> "01010000" """ if minlen < 1: raise ValueError, "a bitstring must have at least 1 char" if n < 0: raise ValueError, "bitstring representation undefined for neg numbers" result = "" while n > 0: if n & 1: result = result + "1" else: result = result + "0" n = n >> 1 if len(result) < minlen: result = result + "0" * (minlen - len(result)) return result def binaryXor(n1, n2): """Return the xor of two bitstrings of equal length as another bitstring of the same length. EXAMPLE: binaryXor("10010", "00011") -> "10001" """ if len(n1) != len(n2): raise ValueError, "can't xor bitstrings of different " + \ "lengths (%d and %d)" % (len(n1), len(n2)) # We assume that they are genuine bitstrings instead of just random # character strings. result = "" for i in range(len(n1)): if n1[i] == n2[i]: result = result + "0" else: result = result + "1" return result def xor(*args): """Return the xor of an arbitrary number of bitstrings of the same length as another bitstring of the same length. EXAMPLE: xor("01", "11", "10") -> "00" """ if args == []: raise ValueError, "at least one argument needed" result = args[0] for arg in args[1:]: result = binaryXor(result, arg) return result def rotateLeft(input, places): """Take a bitstring 'input' of arbitrary length. Rotate it left by 'places' places. Left means that the 'places' most significant bits are taken out and reinserted as the least significant bits. Note that, because the bitstring representation is little-endian, the visual effect is actually that of rotating the string to the right. EXAMPLE: rotateLeft("000111", 2) -> "110001" """ p = places % len(input) return input[-p:] + input[:-p] def rotateRight(input, places): return rotateLeft(input, -places) def shiftLeft(input, p): """Take a bitstring 'input' of arbitrary length. Shift it left by 'p' places. Left means that the 'p' most significant bits are shifted out and dropped, while 'p' 0s are inserted in the the least significant bits. Note that, because the bitstring representation is little-endian, the visual effect is actually that of shifting the string to the right. Negative values for 'p' are allowed, with the effect of shifting right instead (i.e. the 0s are inserted in the most significant bits). EXAMPLE: shiftLeft("000111", 2) -> "000001" shiftLeft("000111", -2) -> "011100" """ if abs(p) >= len(input): # Everything gets shifted out anyway return "0" * len(input) if p < 0: # Shift right instead return input[-p:] + "0" * len(input[:-p]) elif p == 0: return input else: # p > 0, normal case return "0" * len(input[-p:]) + input[:-p] def shiftRight(input, p): """Take a bitstring 'input' and shift it right by 'p' places. See the doc for shiftLeft for more details.""" return shiftLeft(input, -p) # -------------------------------------------------------------- # Hex conversion functions # A hexstring is little-endian and just like a bitstring except that it # uses hex digits (considered as atomic). Example: the hexstring for ten is # "a" (not "5" as some might perversely assume) and the hexstring for 160 # (= 10 * 16) is "0a". Similarly to what happens with the binstring, the # hexstring has the property that the character at position i (indexing # from 0) has weight 16^i. bin2hex = { # Given a 4-char bitstring, return the corresponding 1-char hexstring "0000": "0", "1000": "1", "0100": "2", "1100": "3", "0010": "4", "1010": "5", "0110": "6", "1110": "7", "0001": "8", "1001": "9", "0101": "a", "1101": "b", "0011": "c", "1011": "d", "0111": "e", "1111": "f", } # Make the reverse lookup table too hex2bin = {} for (bin, hex) in bin2hex.items(): hex2bin[hex] = bin def bitstring2hexstring(b): """Take bitstring 'b' and return the corresponding hexstring.""" result = "" l = len(b) if l % 4: b = b + "0" * (4-(l%4)) for i in range(0, len(b), 4): result = result+bin2hex[b[i:i+4]] return result def hexstring2bitstring(h): """Take hexstring 'h' and return the corresponding bitstring.""" result = "" for c in h: result = result + hex2bin[c] return result # A hwseq is not a terribly pure representation but it may be easier for # humans to read (and enter into C programs). It is a string containing as # many 32-bit words as necessary to hold the number. The words are arranged # in little-endian order and are separated by spaces. Each word is # represented as 8 hex digits in big-endian order, prefixed by 0x (i.e. the # format that you'd use in C source code). Example: decimal 10, extended to # 64 bits, is represented as the following hwseq: "0x0000000a 0x00000000". def bitstring2hwseq(b, minWords = 1): """Take bitstring 'b' and return the corresponding hwseq with at least 'minWords' words in it.""" result = "" # Pad b with 0s if needed l = len(b) wordsNeeded = l / 32 if l % 32: wordsNeeded = wordsNeeded + 1 if wordsNeeded < minWords: wordsNeeded = minWords bitsNeeded = wordsNeeded * 32 b = b + "0" * (bitsNeeded-l) for word in range(bitsNeeded/32): result = result + " 0x" for i in range(8): result = result + bin2hex[b[word*32+(7-i)*4:word*32+(8-i)*4]] return result[1:] def hwseq2bitstring(h): """Take hwseq 'h' and transform it into a bitstring. Keep the same number of bits in the representation: don't chop any 0s off the end.""" result = "" h = string.lower(h) while h != "": h = string.strip(h) if len(h) < 8+2: raise ValueError, "Can't find a complete word in this tail: " + h if h[:2] != "0x": raise ValueError, "Expecting 0x, found '%s'" % h[:2] h = h[2:] for i in range(8): d = h[7-i] if not d in hex2bin.keys(): raise ValueError, "Expecting 8 hex digits instead of '%s'"% h[:8] result = result + hex2bin[h[7-i]] h = h[8:] return result # -------------------------------------------------------------- # Format conversions def quadSplit(b128): """Take a 128-bit bitstring and return it as a list of 4 32-bit bitstrings, least significant bitstring first.""" if len(b128) != 128: raise ValueError, "must be 128 bits long, not " + len(b128) result = [] for i in range(4): result.append(b128[(i*32):(i+1)*32]) return result def quadJoin(l4x32): """Take a list of 4 32-bit bitstrings and return it as a single 128-bit bitstring obtained by concatenating the internal ones.""" if len(l4x32) != 4: raise ValueError, "need a list of 4 bitstrings, not " + len(l4x32) return l4x32[0] + l4x32[1] + l4x32[2] + l4x32[3] # -------------------------------------------------- # Self-testing def test1(plainText, userKey): """Return true iff you can decrypt what you encrypted, using normal mode.""" O.show("testTitle", "Normal: can we decrypt what we encrypted?", None, "tu") cipherText = encrypt(plainText, userKey) decryptedText = decrypt(cipherText, userKey) return (plainText == decryptedText) def test2(plainText, userKey): """Return true iff you can decrypt what you encrypted, using bitslice.""" O.show("testTitle", "Bitslice: decrypting what we encrypted?", None, "tu") cipherText = encryptBitslice(plainText, userKey) decryptedText = decryptBitslice(cipherText, userKey) return (plainText == decryptedText) def test3(plainText, userKey): """Return true iff encrypting the same thing with normal and bitslice modes gives the same result.""" O.show("testTitle", "Same results with normal and bitslice?", None, "tu") cipherText = encrypt(plainText, userKey) cipherTextBitslice = encryptBitslice(plainText, userKey) return (cipherText == cipherTextBitslice) def printTest(worked): if worked: print "---Success!---" else: print "***Failure***" # -------------------------------------------------- # Seeing what happens inside class Observer: """An object of this class can selectively display the values of the variables you want to observe while the program is running. There are tags that you can switch on or off. You sprinkle show() statements throughout the program to show the value of a variable at a particular point: show() will display the relevant variable only if the corresponding tag is currently on. The special tag "ALL" forces all show() statements to display their variable.""" typesOfVariable = { "tu": "unknown", "tb": "bitstring", "tlb": "list of bitstrings",} formats = { "fb": "bitstring", "fh": "hexstring", "fhws": "hwseq",} def __init__(self, tags=[], format="fhws"): self.tags = {} for tag in tags: self.tags[tag] = 1 self.format = format def addTag(self, *tags): """Add the supplied tag(s) to those that are currently active, i.e. those that, if a corresponding "show()" is executed, will print something.""" for t in tags: self.tags[t] = 1 def removeTag(self, *tags): """Remove the supplied tag(s) from those currently active.""" for t in tags: if t in self.tags.keys(): del self.tags[t] def setFormat(self, f): """Set the output format to f, which must be one of Observer.formats.""" self.format = f def show(self, tag, variable, label=None, type="tb"): """Conditionally print a message with the current value of 'variable'. The message will only be printed if the supplied 'tag' is among the active ones (or if the 'ALL' tag is active). The 'label', if not null, is printed before the value of the 'variable'; if it is null, it is substituted with the 'tag'. The 'type' of the 'variable' (giving us a clue on how to print it) must be one of Observer.typesOfVariable.""" if label == None: label = tag if "ALL" in self.tags.keys() or tag in self.tags.keys(): if type == "tu": output = `variable` elif type == "tb": output = self._renderBitstring(variable) elif type == "tlb": output = "" for item in variable: output = output + " %s" % self._renderBitstring(item) output = "[" + output[1:] + "]" else: raise ValueError, "unknown type: %s. Valid ones are %s" % ( type, self.typesOfVariable.keys()) print label, if output: print "=", output else: print def _renderBitstring(self, b): """Internal helper function: take a bitstring 'b' and return its string representation according to the currently active format.""" if self.format == "fb": output = b elif self.format == "fh": output = bitstring2hexstring(b) elif self.format == "fhws": output = bitstring2hwseq(b) else: raise ValueError, "unknown format: %s. Valid ones are %s" % ( self.format, self.formats.keys()) return output # We make one global observer object that is always available O = Observer(["plainText", "userKey", "cipherText"]) # -------------------------------------------------------------- # Constants phi = 0x9e3779b9L r = 32 # -------------------------------------------------------------- # Data tables # Each element of this list corresponds to one S-box. Each S-box in turn is # a list of 16 integers in the range 0..15, without repetitions. Having the # value v (say, 14) in position p (say, 0) means that if the input to that # S-box is the pattern p (0, or 0x0) then the output will be the pattern v # (14, or 0xe). SBoxDecimalTable = [ [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7], [0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8], [4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0], [15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13], [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10], [3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5], [0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15], [13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9], [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8], [13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1], [13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7], [1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12], [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15], [13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9], [10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4], [3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14], [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9], [14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6], [4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14], [11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3], [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11], [10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8], [9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6], [4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13], [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1], [13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6], [1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2], [6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12], [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7], [1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2], [7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8], [2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11], ] # Make another version of this table as a list of dictionaries: one # dictionary per S-box, where the value of the entry indexed by i tells you # the output configuration when the input is i, with both the index and the # value being bitstrings. # Make also the inverse: another list of dictionaries, one per S-box, where each # dictionary gets the output of the S-box as the key and gives you the # input, with both values being 4-bit bitstrings. SBoxBitstring = [] SBoxBitstringInverse = [] for line in SBoxDecimalTable: dict = {} inverseDict = {} for i in range(len(line)): index = bitstring(i, 4) value = bitstring(line[i], 4) dict[index] = value inverseDict[value] = index SBoxBitstring.append(dict) SBoxBitstringInverse.append(inverseDict) # The Initial and Final permutations are each represented by one list # containing the integers in 0..127 without repetitions. Having value v # (say, 32) at position p (say, 1) means that the output bit at position p # (1) comes from the input bit at position v (32). IPTable = [ 0, 32, 64, 96, 1, 33, 65, 97, 2, 34, 66, 98, 3, 35, 67, 99, 4, 36, 68, 100, 5, 37, 69, 101, 6, 38, 70, 102, 7, 39, 71, 103, 8, 40, 72, 104, 9, 41, 73, 105, 10, 42, 74, 106, 11, 43, 75, 107, 12, 44, 76, 108, 13, 45, 77, 109, 14, 46, 78, 110, 15, 47, 79, 111, 16, 48, 80, 112, 17, 49, 81, 113, 18, 50, 82, 114, 19, 51, 83, 115, 20, 52, 84, 116, 21, 53, 85, 117, 22, 54, 86, 118, 23, 55, 87, 119, 24, 56, 88, 120, 25, 57, 89, 121, 26, 58, 90, 122, 27, 59, 91, 123, 28, 60, 92, 124, 29, 61, 93, 125, 30, 62, 94, 126, 31, 63, 95, 127, ] FPTable = [ 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 124, 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125, 2, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62, 66, 70, 74, 78, 82, 86, 90, 94, 98, 102, 106, 110, 114, 118, 122, 126, 3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51, 55, 59, 63, 67, 71, 75, 79, 83, 87, 91, 95, 99, 103, 107, 111, 115, 119, 123, 127, ] # The Linear Transformation is represented as a list of 128 lists, one for # each output bit. Each one of the 128 lists is composed of a variable # number of integers in 0..127 specifying the positions of the input bits # that must be XORed together (say, 72, 144 and 125) to yield the output # bit corresponding to the position of that list (say, 1). LTTable = [ [16, 52, 56, 70, 83, 94, 105], [72, 114, 125], [2, 9, 15, 30, 76, 84, 126], [36, 90, 103], [20, 56, 60, 74, 87, 98, 109], [1, 76, 118], [2, 6, 13, 19, 34, 80, 88], [40, 94, 107], [24, 60, 64, 78, 91, 102, 113], [5, 80, 122], [6, 10, 17, 23, 38, 84, 92], [44, 98, 111], [28, 64, 68, 82, 95, 106, 117], [9, 84, 126], [10, 14, 21, 27, 42, 88, 96], [48, 102, 115], [32, 68, 72, 86, 99, 110, 121], [2, 13, 88], [14, 18, 25, 31, 46, 92, 100], [52, 106, 119], [36, 72, 76, 90, 103, 114, 125], [6, 17, 92], [18, 22, 29, 35, 50, 96, 104], [56, 110, 123], [1, 40, 76, 80, 94, 107, 118], [10, 21, 96], [22, 26, 33, 39, 54, 100, 108], [60, 114, 127], [5, 44, 80, 84, 98, 111, 122], [14, 25, 100], [26, 30, 37, 43, 58, 104, 112], [3, 118], [9, 48, 84, 88, 102, 115, 126], [18, 29, 104], [30, 34, 41, 47, 62, 108, 116], [7, 122], [2, 13, 52, 88, 92, 106, 119], [22, 33, 108], [34, 38, 45, 51, 66, 112, 120], [11, 126], [6, 17, 56, 92, 96, 110, 123], [26, 37, 112], [38, 42, 49, 55, 70, 116, 124], [2, 15, 76], [10, 21, 60, 96, 100, 114, 127], [30, 41, 116], [0, 42, 46, 53, 59, 74, 120], [6, 19, 80], [3, 14, 25, 100, 104, 118], [34, 45, 120], [4, 46, 50, 57, 63, 78, 124], [10, 23, 84], [7, 18, 29, 104, 108, 122], [38, 49, 124], [0, 8, 50, 54, 61, 67, 82], [14, 27, 88], [11, 22, 33, 108, 112, 126], [0, 42, 53], [4, 12, 54, 58, 65, 71, 86], [18, 31, 92], [2, 15, 26, 37, 76, 112, 116], [4, 46, 57], [8, 16, 58, 62, 69, 75, 90], [22, 35, 96], [6, 19, 30, 41, 80, 116, 120], [8, 50, 61], [12, 20, 62, 66, 73, 79, 94], [26, 39, 100], [10, 23, 34, 45, 84, 120, 124], [12, 54, 65], [16, 24, 66, 70, 77, 83, 98], [30, 43, 104], [0, 14, 27, 38, 49, 88, 124], [16, 58, 69], [20, 28, 70, 74, 81, 87, 102], [34, 47, 108], [0, 4, 18, 31, 42, 53, 92], [20, 62, 73], [24, 32, 74, 78, 85, 91, 106], [38, 51, 112], [4, 8, 22, 35, 46, 57, 96], [24, 66, 77], [28, 36, 78, 82, 89, 95, 110], [42, 55, 116], [8, 12, 26, 39, 50, 61, 100], [28, 70, 81], [32, 40, 82, 86, 93, 99, 114], [46, 59, 120], [12, 16, 30, 43, 54, 65, 104], [32, 74, 85], [36, 90, 103, 118], [50, 63, 124], [16, 20, 34, 47, 58, 69, 108], [36, 78, 89], [40, 94, 107, 122], [0, 54, 67], [20, 24, 38, 51, 62, 73, 112], [40, 82, 93], [44, 98, 111, 126], [4, 58, 71], [24, 28, 42, 55, 66, 77, 116], [44, 86, 97], [2, 48, 102, 115], [8, 62, 75], [28, 32, 46, 59, 70, 81, 120], [48, 90, 101], [6, 52, 106, 119], [12, 66, 79], [32, 36, 50, 63, 74, 85, 124], [52, 94, 105], [10, 56, 110, 123], [16, 70, 83], [0, 36, 40, 54, 67, 78, 89], [56, 98, 109], [14, 60, 114, 127], [20, 74, 87], [4, 40, 44, 58, 71, 82, 93], [60, 102, 113], [3, 18, 72, 114, 118, 125], [24, 78, 91], [8, 44, 48, 62, 75, 86, 97], [64, 106, 117], [1, 7, 22, 76, 118, 122], [28, 82, 95], [12, 48, 52, 66, 79, 90, 101], [68, 110, 121], [5, 11, 26, 80, 122, 126], [32, 86, 99], ] # The following table, necessary for the non-bitslice decryption, doesn't # come from the paper (although it would make a good addition to it). I # derived it with a separate program that basically took a vector of [0, 1, # ..., 127] and applied to it the three transformations defined by FP, the # equations-based inverse LT, and IP. LTTableInverse = [ [53, 55, 72], [1, 5, 20, 90], [15, 102], [3, 31, 90], [57, 59, 76], [5, 9, 24, 94], [19, 106], [7, 35, 94], [61, 63, 80], [9, 13, 28, 98], [23, 110], [11, 39, 98], [65, 67, 84], [13, 17, 32, 102], [27, 114], [1, 3, 15, 20, 43, 102], [69, 71, 88], [17, 21, 36, 106], [1, 31, 118], [5, 7, 19, 24, 47, 106], [73, 75, 92], [21, 25, 40, 110], [5, 35, 122], [9, 11, 23, 28, 51, 110], [77, 79, 96], [25, 29, 44, 114], [9, 39, 126], [13, 15, 27, 32, 55, 114], [81, 83, 100], [1, 29, 33, 48, 118], [2, 13, 43], [1, 17, 19, 31, 36, 59, 118], [85, 87, 104], [5, 33, 37, 52, 122], [6, 17, 47], [5, 21, 23, 35, 40, 63, 122], [89, 91, 108], [9, 37, 41, 56, 126], [10, 21, 51], [9, 25, 27, 39, 44, 67, 126], [93, 95, 112], [2, 13, 41, 45, 60], [14, 25, 55], [2, 13, 29, 31, 43, 48, 71], [97, 99, 116], [6, 17, 45, 49, 64], [18, 29, 59], [6, 17, 33, 35, 47, 52, 75], [101, 103, 120], [10, 21, 49, 53, 68], [22, 33, 63], [10, 21, 37, 39, 51, 56, 79], [105, 107, 124], [14, 25, 53, 57, 72], [26, 37, 67], [14, 25, 41, 43, 55, 60, 83], [0, 109, 111], [18, 29, 57, 61, 76], [30, 41, 71], [18, 29, 45, 47, 59, 64, 87], [4, 113, 115], [22, 33, 61, 65, 80], [34, 45, 75], [22, 33, 49, 51, 63, 68, 91], [8, 117, 119], [26, 37, 65, 69, 84], [38, 49, 79], [26, 37, 53, 55, 67, 72, 95], [12, 121, 123], [30, 41, 69, 73, 88], [42, 53, 83], [30, 41, 57, 59, 71, 76, 99], [16, 125, 127], [34, 45, 73, 77, 92], [46, 57, 87], [34, 45, 61, 63, 75, 80, 103], [1, 3, 20], [38, 49, 77, 81, 96], [50, 61, 91], [38, 49, 65, 67, 79, 84, 107], [5, 7, 24], [42, 53, 81, 85, 100], [54, 65, 95], [42, 53, 69, 71, 83, 88, 111], [9, 11, 28], [46, 57, 85, 89, 104], [58, 69, 99], [46, 57, 73, 75, 87, 92, 115], [13, 15, 32], [50, 61, 89, 93, 108], [62, 73, 103], [50, 61, 77, 79, 91, 96, 119], [17, 19, 36], [54, 65, 93, 97, 112], [66, 77, 107], [54, 65, 81, 83, 95, 100, 123], [21, 23, 40], [58, 69, 97, 101, 116], [70, 81, 111], [58, 69, 85, 87, 99, 104, 127], [25, 27, 44], [62, 73, 101, 105, 120], [74, 85, 115], [3, 62, 73, 89, 91, 103, 108], [29, 31, 48], [66, 77, 105, 109, 124], [78, 89, 119], [7, 66, 77, 93, 95, 107, 112], [33, 35, 52], [0, 70, 81, 109, 113], [82, 93, 123], [11, 70, 81, 97, 99, 111, 116], [37, 39, 56], [4, 74, 85, 113, 117], [86, 97, 127], [15, 74, 85, 101, 103, 115, 120], [41, 43, 60], [8, 78, 89, 117, 121], [3, 90], [19, 78, 89, 105, 107, 119, 124], [45, 47, 64], [12, 82, 93, 121, 125], [7, 94], [0, 23, 82, 93, 109, 111, 123], [49, 51, 68], [1, 16, 86, 97, 125], [11, 98], [4, 27, 86, 97, 113, 115, 127], ] # -------------------------------------------------- # Handling command line arguments and stuff help = """ Serpent Reference Implementation written by Frank Stajano http://www.cl.cam.ac.uk/~fms27/ Cambridge University Computer Laboratory $Id: SERPREF.PY,v 1.15 1998/03/05 16:46:27 fms Exp fms $ Serpent cipher by Eli Biham, Ross Anderson, Lars Knudsen Encrypts or decrypts one block of data using the Serpent cipher and optionally showing you what's going on inside at the various stages of the computation. SYNTAX: serpref mode [options] MODE is one of the following: -e -> encrypt -d -> decrypt -s -> self-test -h -> help (the text you're reading right now) OPTIONS are: -f format -> The format in which the long numbers are expressed (both for input and for output). There are three formats: "b" for bitstring (little- endian sequence of 0 and 1); "h" for hexstring (little-endian sequence of hex digits); "hws" for hex word sequence (little-endian sequence of C-style 32-bit words, each printed in big-endian format as "0x" followed by 8 hex digits, with one space between words). The default is "hws". Optional. -p plainText -> The 128-bit value to be encrypted, expressed in the format specified by -f. Required in mode -e, optional in mode -s. Ignored otherwise. -c cipherText -> The 128-bit value to be decrypted, expressed in the format specified by -f. Required in mode -d. Ignored otherwise. -k key -> The 256-bit value of the key, expressed in the format specified by -f. Required in modes -e and -d, optional in mode -s. -t tagName -> Turn on the observer tag with that name. This means that any observer messages associated with this tag will now be displayed. This option may be specified several times to add multiple tags. The special tag ALL turns on all the messages. -b -> Use the bitslice version instead of the traditional version, which is otherwise used by default. Optional in modes -e and -d. Ignored otherwise. NOTE: when using the (default) "hws" format, where values contain spaces, be sure to use quoting so that this program receives the entire value as one argument. TAGS: These are the tags of the quantities you can currently observe with -t. Names are modelled on the paper's notation. For the non-bitslice: BHati xored SHati BHatiPlus1 wi KHati For the bitslice: Bi xored Si BiPlus1 wi Ki Generic: plainText userKey cipherText testTitle fnTitle I/O FORMAT: All the I/O formats used by serpref (-f b for bitstring, -f h for hexstring, -f hws for hex word sequence) are little-endian: whatever the basic chunk is (respectively: a bit, a 4-bit nibble or a 32-bit word), if it occurs in position 'i' then its weight is N^i (with N being respectively 2, 2^4, 2^32). As an example, the number ten extended to 64 bits is expressed like this: -f b "0101000000000000000000000000000000000000000000000000000000000000" -f h "a00000000000000" -f hws "0x0000000a 0x00000000" Note that the hws format always requires you to use 8 hex digits per word even if C would allow you to write the third example as "0xa 0x0". Individual words in the hws format are in fact big-endian, for compatibility with the C I/O library. USAGE EXAMPLES: serpref -s Runs a self-test (made of three sub-tests) on a randomly chosen plaintext and key. The tests compare encryption/decription and traditional/bitslice. serpref -s -k 0x0000000d -p 0x00000011 Runs the self-test on the key "13" and on the plaintext "17". serpref -s -k 1011 -p 10001 -f b Runs the self-test on the key "13" and on the plaintext "17", but using bitstrings as the input/output format. serpref -s -k 0x0000000d -p "0x00000011 0x00000001" Runs the self-test on the key "13" and on the plaintext "17+2^32" (however much that is). serpref -e -k "0x32158636 0x0da0aa51 0x97db1144 0x44cf2c28 0x7c3fb76d 0x987257da 0xdafd0f29 0x7bf6334d" -p "0x650cba82 0xffd10f30 0xf645ba29 0x6f195106" A realistic example (imagine it all on one line) in which we supply a full 256 bit key and a full 128 bit plaintext. The -e requests an encryption. serpref -e -k "0x32158636 0x0da0aa51 0x97db1144 0x44cf2c28 0x7c3fb76d 0x987257da 0xdafd0f29 0x7bf6334d" -p "0x650cba82 0xffd10f30 0xf645ba29 0x6f195106" -b Same as above, but the extra -b requests bitslice operation. As things are, we won't notice the difference, but see below... serpref -e -k "0x32158636 0x0da0aa51 0x97db1144 0x44cf2c28 0x7c3fb76d 0x987257da 0xdafd0f29 0x7bf6334d" -p "0x650cba82 0xffd10f30 0xf645ba29 0x6f195106" -b -t Bi Same as above, but the "-t Bi" prints out all the intermediate results with a tag of Bi, allowing you to see what happens inside the rounds. Compare this with the following... serpref -e -k "0x32158636 0x0da0aa51 0x97db1144 0x44cf2c28 0x7c3fb76d 0x987257da 0xdafd0f29 0x7bf6334d" -p "0x650cba82 0xffd10f30 0xf645ba29 0x6f195106" -t BHati Same as above except that we are back to the non-bitslice version (there is no -b) and we are printing the items with the BHati tag (which is the equivalent of Bi for the non-bitslice version). serpref -e -k "0x32158636 0x0da0aa51 0x97db1144 0x44cf2c28 0x7c3fb76d 0x987257da 0xdafd0f29 0x7bf6334d" -p "0x650cba82 0xffd10f30 0xf645ba29 0x6f195106" -t xored -t SHati -t BHati Same as above but we are requesting even more details, basically looking at all the intermediate results of each round as well. (You could use the single magic tag -t ALL if you didn't want to have to find out the names of the individual tags.) """ def helpExit(message = None): print help if message: print "ERROR:", message sys.exit() def convertToBitstring(input, inputFormat, numBits): """Take a string 'input', theoretically in the format described by 'inputFormat' (one of Observer.formats) but in practice liable to contain any sort of crap since it's user supplied, and return its bitstring representation, normalised to numBits bits. Raise the appropriate variant of ValueError (with explanatory message) if anything can't be done (this includes the case where the 'input', while otherwise syntactically correct, can't be represented in 'numBits' bits).""" if inputFormat == "fb": if re.match("^[01]+$", input): bitstring = input else: raise ValueError, "%s is not a valid bitstring" % input elif inputFormat == "fh": if re.match("^[0-9a-f]+$", input): bitstring = hexstring2bitstring(input) else: raise ValueError, "%s is not a valid hexstring" % input elif inputFormat == "fhws": re_word = "(0x" + "[0-9a-f]"*8 + ")" if re.match("^" + re_word + "( " + re_word + ")*$", input): bitstring = hwseq2bitstring(input) else: raise ValueError, "%s is not a valid hwseq" % input else: raise ValueError, "invalid input format: %s (must be one of %s)" % ( inputFormat, Observer.formats) # assert: bitstring now contains the bitstring version of the input if len(bitstring) > numBits: # Last chance: maybe it's got some useless 0s... if re.match("^0+$", bitstring[numBits:]): bitstring = bitstring[:numBits] else: raise ValueError, "input too large to fit in %d bits" % numBits else: bitstring = bitstring + "0" * (numBits-len(bitstring)) return bitstring def randomBitstring(numBits): """Return a random bitstring of length 'numBits'.""" result = "" # I don't do it in 32-bit chunks or I'd have problems with the sign bit # in randint. for i in range(numBits/30 + 1): result = result + bitstring(whrandom.randint(0, 0x3fffffff), 30) return result[:numBits] def main(): optList, rest = getopt.getopt(sys.argv[1:], "edshbt:f:k:p:c:") if rest: helpExit("Sorry, can't make sense of this: '%s'" % rest) # Transform the list of options into a more comfortable # dictionary. This only works with non-repeated options, though, so # tags (which are repeated) must be dealt with separately. options = {} for key, value in optList: if key == "-t": O.addTag(value) else: if key in options.keys(): helpExit("Multiple occurrences of " + key) else: options[string.strip(key)] = string.strip(value) # Not more than one mode mode = None for k in options.keys(): if k in ["-e", "-d", "-s", "-h"]: if mode: helpExit("you can only specify one mode") else: mode = k if not mode: helpExit("No mode specified") # Determine the number format if options.has_key("-f"): if options["-f"] in ["b", "h", "hws"]: format = "f" + options["-f"] else: helpExit("-f (format) can only be one of b, h or hws") else: format = "fhws" O.setFormat(format) # Put plainText, userKey, cipherText in bitstring format. plainText = userKey = cipherText = None if options.has_key("-k"): userKey = convertToBitstring(options["-k"], format, 256) if options.has_key("-p"): plainText = convertToBitstring(options["-p"], format, 128) if options.has_key("-c"): cipherText = convertToBitstring(options["-c"], format, 128) if mode == "-e" or mode == "-d": if not userKey: helpExit("-k (key) required when doing -e (encrypt) or -d (decrypt)") if mode == "-e": if not plainText: helpExit("-p (plaintext) is required when doing -e (encrypt)") if mode == "-d": if not cipherText: helpExit("-c (ciphertext) is required when doing -d (decrypt)") # Make up random key and plaintext if missing for self test if mode == "-s": if not plainText: plainText = randomBitstring(128) if not userKey: userKey = randomBitstring(256) # Perform the action specified by the mode # NOTE that the observer will automatically print the basic stuff such # as plainText, userKey and cipherText (in the right format too), so we # only need to perform the action, without adding any extra print # statements here. if mode == "-e": if options.has_key("-b"): cipherText = encryptBitslice(plainText, userKey) else: cipherText = encrypt(plainText, userKey) elif mode == "-d": if options.has_key("-b"): plainText = decryptBitslice(cipherText, userKey) else: plainText = decrypt(cipherText, userKey) elif mode == "-s": O.addTag("testTitle", "fnTitle") printTest(test1(plainText, userKey)) printTest(test2(plainText, userKey)) printTest(test3(plainText, userKey)) else: helpExit() if __name__ == "__main__": main()

HTML 4.0/CSS generated by Frank Stajano's html-pretty-print
for Emacs.

If you view this page in a browser with Cascading Style
Sheets enabled, the listing appears beautified. Besides, the markup is
parametric and you can change the font characteristics of the various
syntactical elements by simply redefining the style sheet.