Mission6.sagews

#Question 6
S1=[[1,0,1],[0,1,0],[0,0,1],[1,1,0],[0,1,1],[1,0,0],[1,1,1],[0,0,0],
    [0,0,1],[1,0,0],[1,1,0],[0,1,0],[0,0,0],[1,1,1],[1,0,1],[0,1,1]]
S2=[[1,0,0],[0,0,0],[1,1,0],[1,0,1],[1,1,1],[0,0,1],[0,1,1],[0,1,0],
    [1,0,1],[0,1,1],[0,0,0],[1,1,1],[1,1,0],[0,1,0],[0,0,1],[1,0,0]]

def Expander(L): #Expands a string from 6 bits to 8 bits for SDES
    if not len(L)==6:
        print "Wrong length"
        return 0
    R = [L[0],L[1],L[3],L[2],L[3],L[2],L[4],L[5]]
    return R

def xor(L,M):  #performs a binary xor (addition) of the two strings L,M
    if not len(L)==len(M):
        print "Strings have different lengths"
        return 0
    return [sum(a)%2 for a in zip(L,M)]

def roundkey(K,i): #Return the 8 bit key for round i from the master 9-bit key
    if i==1 or i==2:
        return K[i-1:i+7]
    else:
        return K[i-1:10]+K[0:i-2]

def bin2int(L): #convert binary list to integer
    sum=0
    l=len(L)-1
    for i in [0..l]:
        if L[i]==1:
            sum+=2^(l-i)
    return sum

def split(M):  #Splits the list M into two equal halves, used several times in SDES algorithm
    if len(M)%2==1:
        print "Wrong Message Length"
    return (M[0:len(M)/2],M[len(M)/2:len(M)])

def SDESf(R,Ki): #Performs the function f that is used in the encryption of SDES
    E=Expander(R)
    Temp=xor(E,Ki)
    (rhalf,lhalf)=split(Temp)
    return S1[bin2int(rhalf)]+S2[bin2int(lhalf)]

def SDESround(M,Kr):  #Performs one round of SDES using the roundkey Kr
    (L1,R1)=split(M)
    L2=R1
    R2 = xor(SDESf(R1,Kr),L1)
    return L2+R2

def SDES(M,K,r):  #Performs SDES on M with the key K using r rounds.
    for i in [1..r]:
        rkey=roundkey(K,i)
        M=SDESround(M,rkey)
        print "Round:",i,M
    return M

#Example:
SDES([1,0,0,1,0,0,1,0,0,1,0,0],[1,1,1,1,1,1,1,1,0],7)

Error in lines 1-1 Traceback (most recent call last): File "/cocalc/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 996, in execute exec compile(block+'\n', '', 'single') in namespace, locals File "", line 1, in <module> NameError: name 'SDES' is not defined