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Image: ubuntu2204
Kernel: SageMath 10.1
n = 255 F.<alpha> = GF(n+1, 'a', modulus='primitive') assert alpha.multiplicative_order() == n R.<s> = F['s'] # example of searching for roots in this polynomial ring # print((s**2 * (s-1)).roots()) # consult ?s.roots for more help k = 223 t = n - k generator_poly = prod([s - alpha**j for j in range(1, t+1)]) received_bytes = b'O\x04\xc0A\xd1\xceY\x05\xb44\xda\xf6\xe5F_V\xd1N\xf9\xc2\xe2\x01l\xc2\xbb\xf0w:\x01\x8bw\xaa\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\xab\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x8b\x1d\x1e\x1f !"#$%&\'()*\xa3,-./0123456789C;<=>?@ABCDEFGH#JKLMNOPQRSTUVW\x03YZ[\\]^_`abcdef+hijklmnopqrstuKwxyz{|}~\x7f\x80\x81\x82\x83\x84\xab\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x8b\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xb3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb3\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde' # produce the error locations and error values in this message
# Given parameters n = 255 F.<alpha> = GF(n+1, 'a', modulus='primitive') assert alpha.multiplicative_order() == n R.<s> = F['s'] # example of searching for roots in this polynomial ring # print((s**2 * (s-1)).roots()) # consult ?s.roots for more help # Calculate the number of errors to correct k = 223 t = n - k # Generate the generator polynomial for Reed-Solomon code generator_poly = prod([s - alpha**j for j in range(1, t+1)]) # Example received message received_bytes = b'O\x04\xc0A\xd1\xceY\x05\xb44\xda\xf6\xe5F_V\xd1N\xf9\xc2\xe2\x01l\xc2\xbb\xf0w:\x01\x8bw\xaa\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\xab\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x8b\x1d\x1e\x1f !"#$%&\'()*\xa3,-./0123456789C;<=>?@ABCDEFGH#JKLMNOPQRSTUVW\x03YZ[\\]^_`abcdef+hijklmnopqrstuKwxyz{|}~\x7f\x80\x81\x82\x83\x84\xab\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x8b\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xb3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb3\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde' # Converting receiving bytes to a polynomial received_polynomial = sum([Integer(received_bytes[i]) * s**i for i in range(len(received_bytes))]) # Calculating syndromes by evaluating the received polynomial at powers of alpha syndromes = [received_polynomial(alpha**i) for i in range(1, n-k+1)] # Finding error locator polynomial using Berlekamp-Massey algorithm err_locator = berlekamp_massey(syndromes, F) # Finding error locations by calculating the roots of the error locator polynomial err_locations = err_locator.roots() # Finding error values by evaluating error evaluator polynomial at error locations err_values = [received_polynomial(alpha**(-i)) for i in err_locations] # Correcting errors in received polynomial correct_polynomial = received_polynomial - sum([err_values[i] * s**(-err_locations[i]) for i in range(len(err_locations))]) # Converting corrected polynomial to bytes correct_bytes = bytes([int(correct_polynomial.coefficient(s, i)) for i in range(len(received_bytes))]) # Printing error locations and values: print("Error Locations:", err_locations) print("Error Values:", err_values) print("Corrected Message:", correct_bytes)
--------------------------------------------------------------------------- NameError Traceback (most recent call last) Cell In [3], line 28 25 syndromes = [received_polynomial(alpha**i) for i in range(Integer(1), n-k+Integer(1))] 27 # Find the error locator polynomial using Berlekamp-Massey algorithm ---> 28 err_locator = berlekamp_massey(syndromes, F) 30 # Find the error locations by calculating the roots of the error locator polynomial 31 err_locations = err_locator.roots() NameError: name 'berlekamp_massey' is not defined