| 0,0 → 1,38 |
|---|
| """ prf_dot11.py |
| |
| The PRF function is used in a number of places in 802.11i |
| to create psuedo random octet strings. |
| |
| The parameter 'prefix' is a string that shall be a unique label for each |
| different purpose of the PRF. |
| """ |
| |
| import hmac, sha # available in any Python 2.x |
| |
| def PRF( key, prefix, data, number_of_bits): |
| """ Key, prefix and data are arbitrary strings . |
| number_of_bits must be a multiple of 8 |
| HMAC_SHA1 generates 20 byte blocks. Enough are generated to get the |
| requested number of octets and the reslut is truncated to the requested size. |
| """ |
| number_of_octets, remainder = divmod(number_of_bits,8) |
| if remainder != 0: |
| raise ValueError, 'requested bits not multiple of 8' |
| R = '' |
| i = 0 |
| while len(R) <= number_of_octets : |
| hmac_sha_1= hmac.new( key, prefix + chr(0x00) + data + chr(i), sha ) |
| i = i + 1 |
| R = R + hmac_sha_1.digest() # concatenate latest hash to result string |
| return R[:number_of_octets] # return R truncated to 'number_of_octets' |
| |
| def PRF_128(key,A,B): return PRF(key,A,B,128) |
| def PRF_192(key,A,B): return PRF(key,A,B,192) |
| def PRF_256(key,A,B): return PRF(key,A,B,256) |
| def PRF_384(key,A,B): return PRF(key,A,B,384) |
| def PRF_512(key,A,B): return PRF(key,A,B,512) |
| def PRF_768(key,A,B): return PRF(key,A,B,768) |
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