[op25-dev] Re: RC4

This is merely a historical archive of years 2008-2021, before the migration to mailman3.

A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/op25-dev@lists.osmocom.org/.

Steve Glass stevie.glass@gmail.com [op25-dev] op25-dev at yahoogroups.com
Tue Feb 10 14:20:13 UTC 2015


In fairness, the code Matt linked to above was the stuff I used to
recover the bit scheduling of the RC4 cipher. I'd forgotten that it was
even online :)

Turns out P25 adopts a really simple scheme and throws away RC4
ciphertext octets exactly where you'd expect it to (compare it with
DES/OFB which has a similar structure and throws away ciphertext octets
at the same position). The only difference is that P25 skips the first
256 octets of the ciphertext because of a known weakness in RC4.

Would be great to see auto-recovery; even manual key entry would be
cool. I'm unlikely to look at it soon as I'm up to my neck in GSM right now!

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 931 bytes
Desc: OpenPGP digital signature
URL: <http://lists.osmocom.org/pipermail/op25-dev/attachments/20150211/f4412912/attachment.bin>


More information about the op25-dev mailing list