02 Fixed XOR

Challenge

Write a function that takes two equal-length buffers and produces their XOR combination.

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Script

def xor(a,b):
    if len(a) != len(b):
        return -1
    c = ''
    for i in range(len(a)):
        c += chr(ord(a[i]) ^ ord(b[i]))
    return c

if __name__ == '__main__':
    s1 = '1c0111001f010100061a024b53535009181c'.decode('hex')
    s2 = '686974207468652062756c6c277320657965'.decode('hex')
    result = xor(s1, s2)
    print result.encode('hex') 

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Result