7e55241233
Initial import of HDCP key generating code. This code only generates a source key for the moment.
89 lines
2.5 KiB
Python
Executable File
89 lines
2.5 KiB
Python
Executable File
#!/usr/bin/env python
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import string, random
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MASTER_KEY_SRC = 'master-key.txt'
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def read_key_file(filelike):
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"""Read a HDCP master key from a key file.
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The key file is formatted into 40*40 56-bit hex values separated by
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white space. The first 40 values correspond to row 1 of the matrix, the
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next 40 row 2, etc. Lines beginning with a '#' are ignored. """
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key_matrix = [ [] ]
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for line in filelike:
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if line[0] == '#':
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# This is a comment... skip
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continue
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# split the line into words and parse the hex
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for entry in map(lambda x: int(x, 16), string.split(line)):
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# do we need to start a new row?
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if len(key_matrix[-1]) >= 40:
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key_matrix.append([])
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# append this entry to the row
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key_matrix[-1].append(entry)
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# check we read the right number of entries in total
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assert( len(key_matrix) == 40 )
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assert( len(key_matrix[-1]) == 40 )
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return key_matrix
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def gen_source_key(key_matrix):
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"""Generate a source key from the master key matrix passed.
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To generate a source key, take a forty-bit number that (in binary)
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consists of twenty ones and twenty zeroes; this is the source KSV. Add
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together those twenty rows of the matrix that correspond to the ones in
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the KSV (with the lowest bit in the KSV corresponding to the first
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row), taking all elements modulo two to the power of fifty-six; this is
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the source private key."""
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# generate KSV - 20 1s and 20 0s
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ksv = (['1'] * 20) + (['0'] * 20)
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# permute KSV
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random.shuffle(ksv)
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# convert the binary to int
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ksv_val = int(string.join(ksv, ''), 2)
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# zip the master key matrix and the ksv s.t. the LSB of KSV is associated with
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# the first row, etc. Then filter to only select those rows where the
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# appropriate bit of the KSV is 1.
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ksv.reverse()
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master_rows = map(lambda x: x[1], filter(lambda x: x[0] == '1', zip(ksv, key_matrix)))
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# now generate the key
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key = [0] * 40
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for row in master_rows:
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# add row to key
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key = map(lambda x: (x[0] + x[1]) & 0xffffffffffffff, zip(key, row))
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return (ksv_val, key)
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def output_human_readable(ksv, key):
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"""Print a human readable version of the KSV and key.
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The KSV is a single integer. The key is a list of 40 integers."""
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# output the ksv
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print 'KSV:'
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print '%010x' % ksv
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# output the key
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key_strs = map(lambda x: '%014x' % x, key)
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print '\nKey:'
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print string.join(map(lambda x: string.join(x, ' '), zip(*[key_strs]*5)), '\n')
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# read the master key file
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key_matrix = read_key_file(open(MASTER_KEY_SRC))
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# generate a source key and output it
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output_human_readable(*gen_source_key(key_matrix))
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