def computeDelta(matlabEng, arrData_bin_1, n, k, m, strCoder):
"""
compute the delta for reconciliation
"""
# find corresponding codeword of data 1
arrMsg_bin_1 = None
arrCodeword_bin_1 = None
if(strCoder == CODER_GOLAY):
n = 23
k = 12
arrMsg_bin_1 = golay.decode(matlabEng, arrData_bin_1, n)
arrCodeword_bin_1 = golay.encode(matlabEng, arrMsg_bin_1, k)
elif (strCoder == CODER_RS):
arrMsg_bin_1 = rs.decode(matlabEng, arrData_bin_1, n, k, m)
arrCodeword_bin_1 = rs.encode(matlabEng, arrMsg_bin_1, n, k, m)
elif(strCoder == CODER_HAMMING):
arrMsg_bin_1 = fec.decode(matlabEng, arrData_bin_1,
n, k, strCoder)
arrCodeword_bin_1 = fec.encode(matlabEng, arrMsg_bin_1,
n, k, strCoder)
else:
raise ValueError("Unkown coder")
# compute the difference
arrDelta = np.bitwise_xor(arrData_bin_1, arrCodeword_bin_1)
return arrDelta
def reconciliate(matlabEng, arrDelta, arrData_bin_2, n, k, m, strCoder):
"""
Given the delta, try to deduce data1 via reconciliation
"""
arrMsg_bin_2 = None
arrCodeword_bin_2 = None
if (strCoder == CODER_GOLAY):
n = 23
k = 12
arrMsg_bin_2 = golay.decode(matlabEng,
np.bitwise_xor(arrData_bin_2, arrDelta),
n)
arrCodeword_bin_2 = golay.encode(matlabEng, arrMsg_bin_2, k)
elif (strCoder == CODER_RS):
arrMsg_bin_2 = rs.decode(matlabEng,
np.bitwise_xor(arrData_bin_2, arrDelta),
n, k, m)
arrCodeword_bin_2 = rs.encode(matlabEng, arrMsg_bin_2, n, k, m)
elif (strCoder == CODER_HAMMING):
arrMsg_bin_2 = fec.decode(matlabEng,
np.bitwise_xor(arrData_bin_2, arrDelta),
n, k, strCoder)
arrCodeword_bin_2 = fec.encode(matlabEng, arrMsg_bin_2, n, k)
else:
raise ValueError("Unkown coder")
# deduce data 1 from data 2 + delta
arrDeducedData_bin_1 = np.bitwise_xor(arrCodeword_bin_2, arrDelta)
return arrDeducedData_bin_1
def test_random_secret(matlabEng, n, k, nErrorBits=1):
# data 1
arrData_1 = np.random.randint(0, 2, n)
arrData_bin_1 = ct.toBinaryArray(arrData_1)
print "d1 (%d): "%len(arrData_bin_1), arrData_bin_1
# data2
arrData_bin_2 = np.copy(arrData_bin_1)
# introduce some errors
arrErrorPos = np.random.choice(range(len(arrData_bin_2)), nErrorBits,
replace=False)
for i in arrErrorPos:
arrData_bin_2[i] = (arrData_bin_2[i] + 1)%2
print "d2 (%d): "%len(arrData_bin_1), arrData_bin_2
# create secret at random
arrSecret = np.random.randint(0, 2, k)
arrSecret_bin = ct.toBinaryArray(arrSecret)
arrCodeword_bin = fec.encode(matlabEng, arrSecret_bin,
n, k, 'hamming/binary')
# compute the difference
arrDelta = np.bitwise_xor(arrData_bin_1, arrCodeword_bin)
# deduce securet
arrCodeword_bin_2 = np.bitwise_xor(arrData_bin_2, arrDelta)
arrSecret_bin_2 = fec.decode(matlabEng, arrCodeword_bin_2,
n, k, 'hamming/binary')
# compute the BER
nMismatchedBits = np.size(arrSecret_bin) - \
np.sum(arrSecret_bin==arrSecret_bin_2)
print "error bit=", nMismatchedBits, ", BER=",\
nMismatchedBits*1.0/np.size(arrSecret_bin)
