Changed decryption block to use osmo_a5 function, in preparation for issue 85
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@ -1,392 +0,0 @@
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/*
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* A pedagogical implementation of the GSM A5/1 and A5/2 "voice privacy"
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* encryption algorithms.
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*
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* Copyright (C) 1998-1999: Marc Briceno, Ian Goldberg, and David Wagner
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*
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* The source code below is optimized for instructional value and clarity.
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* Performance will be terrible, but that's not the point.
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*
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* This software may be export-controlled by US law.
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*
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* This software is free for commercial and non-commercial use as long as
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* the following conditions are adhered to.
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* Copyright remains the authors' and as such any Copyright notices in
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* the code are not to be removed.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
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* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
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* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* The license and distribution terms for any publicly available version
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* or derivative of this code cannot be changed. i.e. this code cannot
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* simply be copied and put under another distribution license
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* [including the GNU Public License].
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*
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* Background: The Global System for Mobile communications is the most
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* widely deployed digital cellular telephony system in the world. GSM
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* makes use of four core cryptographic algorithms, none of which has
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* been published by the GSM MOU. This failure to subject the
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* algorithms to public review is all the more puzzling given that over
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* 215 million GSM subscribers are expected to rely on the claimed
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* security of the system.
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*
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* The four core GSM cryptographic algorithms are:
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* A3 authentication algorithm
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* A5/1 "stronger" over-the-air voice-privacy algorithm
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* A5/2 "weaker" over-the-air voice-privacy algorithm
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* A8 voice-privacy key generation algorithm
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*
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* In April of 1998, our group showed that COMP128, the algorithm used by the
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* overwhelming majority of GSM providers for both A3 and A8 functionality
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* is fatally flawed and allows for cloning of GSM mobile phones.
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*
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* Furthermore, we demonstrated that all A8 implementations we could locate,
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* including the few that did not use COMP128 for key generation, had been
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* deliberately weakened by reducing the keyspace from 64 bits to 54 bits.
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* The remaining 10 bits are simply set to zero!
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*
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* See http://www.scard.org/gsm for additional information.
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*
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* [May 1999]
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* One question so far unanswered is if A5/1, the "stronger" of the two
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* widely deployed voice-privacy algorithm is at least as strong as the
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* key. Meaning: "Does A5/1 have a work factor of at least 54 bits"?
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* Absent a publicly available A5/1 reference implementation, this question
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* could not be answered. We hope that our reference implementation below,
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* which has been verified against official A5/1 test vectors, will provide
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* the cryptographic community with the base on which to construct the
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* answer to this important question.
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*
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* Initial indications about the strength of A5/1 are not encouraging.
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* A variant of A5, while not A5/1 itself, has been estimated to have a
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* work factor of well below 54 bits. See http://jya.com/crack-a5.htm for
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* background information and references.
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*
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* With COMP128 broken and A5/1 published below, we will now turn our
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* attention to A5/2.
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*
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* [August 1999]
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* 19th Annual International Cryptology Conference - Crypto'99
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* Santa Barbara, California
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*
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* A5/2 has been added to the previously published A5/1 source. Our
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* implementation has been verified against official test vectors.
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*
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* This means that our group has now reverse engineered the entire set
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* of cryptographic algorithms used in the overwhelming majority of GSM
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* installations, including all the over-the-air "voice privacy" algorithms.
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*
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* The "voice privacy" algorithm A5/2 proved especially weak. Which perhaps
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* should come as no surprise, since even GSM MOU members have admitted that
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* A5/2 was designed with heavy input by intelligence agencies to ensure
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* breakability. Just how insecure is A5/2? It can be broken in real time
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* with a work factor of a mere 16 bits. GSM might just as well use no "voice
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* privacy" algorithm at all.
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*
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* We announced the break of A5/2 at the Crypto'99 Rump Session.
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* Details will be published in a scientific paper following soon.
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*
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*
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* -- Marc Briceno <marc@scard.org>
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* Voice: +1 (925) 798-4042
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*
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*/
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#ifndef A5_1_2_H
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#define A5_1_2_H
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#include <stdio.h>
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/* Masks for the shift registers */
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#define R1MASK 0x07FFFF /* 19 bits, numbered 0..18 */
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#define R2MASK 0x3FFFFF /* 22 bits, numbered 0..21 */
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#define R3MASK 0x7FFFFF /* 23 bits, numbered 0..22 */
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#ifdef A5_2
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#define R4MASK 0x01FFFF /* 17 bits, numbered 0..16 */
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#endif /* A5_2 */
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#ifndef A5_2
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/* Middle bit of each of the three shift registers, for clock control */
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#define R1MID 0x000100 /* bit 8 */
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#define R2MID 0x000400 /* bit 10 */
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#define R3MID 0x000400 /* bit 10 */
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#else /* A5_2 */
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/* A bit of R4 that controls each of the shift registers */
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#define R4TAP1 0x000400 /* bit 10 */
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#define R4TAP2 0x000008 /* bit 3 */
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#define R4TAP3 0x000080 /* bit 7 */
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#endif /* A5_2 */
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/* Feedback taps, for clocking the shift registers.
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* These correspond to the primitive polynomials
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* x^19 + x^5 + x^2 + x + 1, x^22 + x + 1,
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* x^23 + x^15 + x^2 + x + 1, and x^17 + x^5 + 1. */
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#define R1TAPS 0x072000 /* bits 18,17,16,13 */
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#define R2TAPS 0x300000 /* bits 21,20 */
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#define R3TAPS 0x700080 /* bits 22,21,20,7 */
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#ifdef A5_2
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#define R4TAPS 0x010800 /* bits 16,11 */
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#endif /* A5_2 */
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typedef unsigned char byte;
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typedef unsigned long word;
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typedef word bit;
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/* Calculate the parity of a 32-bit word, i.e. the sum of its bits modulo 2
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*/
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bit parity(word x)
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{
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x ^= x >> 16;
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x ^= x >> 8;
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x ^= x >> 4;
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x ^= x >> 2;
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x ^= x >> 1;
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return x&1;
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}
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/* Clock one shift register. For A5/2, when the last bit of the frame
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* is loaded in, one particular bit of each register is forced to '1';
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* that bit is passed in as the last argument. */
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#ifndef A5_2
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word clockone(word reg, word mask, word taps)
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{
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#else /* A5_2 */
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word clockone(word reg, word mask, word taps, word loaded_bit) {
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#endif /* A5_2 */
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word t = reg & taps;
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reg = (reg << 1) & mask;
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reg |= parity(t);
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#ifdef A5_2
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reg |= loaded_bit;
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#endif /* A5_2 */
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return reg;
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}
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/* The three shift registers. They're in global variables to make the code
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* easier to understand.
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* A better implementation would not use global variables. */
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word R1, R2, R3;
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#ifdef A5_2
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word R4;
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#endif /* A5_2 */
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/* Return 1 iff at least two of the parameter words are non-zero. */
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bit majority(word w1, word w2, word w3) {
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int sum = (w1 != 0) + (w2 != 0) + (w3 != 0);
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if (sum >= 2)
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return 1;
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else
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return 0;
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}
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/* Clock two or three of R1,R2,R3, with clock control
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* according to their middle bits.
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* Specifically, we clock Ri whenever Ri's middle bit
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* agrees with the majority value of the three middle bits. For A5/2,
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* use particular bits of R4 instead of the middle bits. Also, for A5/2,
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* always clock R4.
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* If allP == 1, clock all three of R1,R2,R3, ignoring their middle bits.
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* This is only used for key setup. If loaded == 1, then this is the last
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* bit of the frame number, and if we're doing A5/2, we have to set a
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* particular bit in each of the four registers. */
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void clock(int allP, int loaded) {
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#ifndef A5_2
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bit maj = majority(R1 & R1MID, R2 & R2MID, R3 & R3MID);
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if (allP || (((R1&R1MID) != 0) == maj))
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R1 = clockone(R1, R1MASK, R1TAPS);
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if (allP || (((R2&R2MID) != 0) == maj))
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R2 = clockone(R2, R2MASK, R2TAPS);
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if (allP || (((R3&R3MID) != 0) == maj))
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R3 = clockone(R3, R3MASK, R3TAPS);
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#else /* A5_2 */
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bit maj = majority(R4 & R4TAP1, R4 & R4TAP2, R4 & R4TAP3);
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if (allP || (((R4&R4TAP1) != 0) == maj))
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R1 = clockone(R1, R1MASK, R1TAPS, loaded << 15);
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if (allP || (((R4&R4TAP2) != 0) == maj))
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R2 = clockone(R2, R2MASK, R2TAPS, loaded << 16);
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if (allP || (((R4&R4TAP3) != 0) == maj))
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R3 = clockone(R3, R3MASK, R3TAPS, loaded << 18);
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R4 = clockone(R4, R4MASK, R4TAPS, loaded << 10);
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#endif /* A5_2 */
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}
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/* Generate an output bit from the current state.
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* You grab a bit from each register via the output generation taps;
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* then you XOR the resulting three bits. For A5/2, in addition to
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* the top bit of each of R1,R2,R3, also XOR in a majority function
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* of three particular bits of the register (one of them complemented)
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* to make it non-linear. Also, for A5/2, delay the output by one
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* clock cycle for some reason. */
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bit getbit() {
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bit topbits = (((R1 >> 18) ^ (R2 >> 21) ^ (R3 >> 22)) & 0x01);
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#ifndef A5_2
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return topbits;
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#else /* A5_2 */
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static bit delaybit = 0;
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bit nowbit = delaybit;
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delaybit = (
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topbits
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^ majority(R1 & 0x8000, (~R1) & 0x4000, R1 & 0x1000)
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^ majority((~R2) & 0x10000, R2 & 0x2000, R2 & 0x200)
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^ majority(R3 & 0x40000, R3 & 0x10000, (~R3) & 0x2000)
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);
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return nowbit;
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#endif /* A5_2 */
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}
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/* Do the A5 key setup. This routine accepts a 64-bit key and
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* a 22-bit frame number. */
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void keysetup(byte key_reversed[8], word frame) {
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int i;
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bit keybit, framebit;
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byte key[8];
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for(i=0; i<8; i++){
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key[i] = key_reversed[7-i];
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}
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/* Zero out the shift registers. */
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R1 = R2 = R3 = 0;
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#ifdef A5_2
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R4 = 0;
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#endif /* A5_2 */
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/* Load the key into the shift registers,
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* LSB of first byte of key array first,
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* clocking each register once for every
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* key bit loaded. (The usual clock
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* control rule is temporarily disabled.) */
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for (i = 0; i < 64; i++) {
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clock(1, 0); /* always clock */
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keybit = (key[i/8] >> (i & 7)) & 1; /* The i-th bit of the key */
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R1 ^= keybit;
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R2 ^= keybit;
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R3 ^= keybit;
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#ifdef A5_2
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R4 ^= keybit;
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#endif /* A5_2 */
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}
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/* Load the frame number into the shift registers, LSB first,
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* clocking each register once for every key bit loaded.
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* (The usual clock control rule is still disabled.)
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* For A5/2, signal when the last bit is being clocked in. */
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for (i = 0; i < 22; i++) {
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clock(1, i == 21); /* always clock */
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framebit = (frame >> i) & 1; /* The i-th bit of the frame # */
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R1 ^= framebit;
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R2 ^= framebit;
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R3 ^= framebit;
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#ifdef A5_2
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R4 ^= framebit;
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#endif /* A5_2 */
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}
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/* Run the shift registers for 100 clocks
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* to mix the keying material and frame number
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* together with output generation disabled,
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* so that there is sufficient avalanche.
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* We re-enable the majority-based clock control
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* rule from now on. */
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for (i = 0; i < 100; i++) {
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clock(0, 0);
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}
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/* For A5/2, we have to load the delayed output bit. This does _not_
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* change the state of the registers. For A5/1, this is a no-op. */
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getbit();
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/* Now the key is properly set up. */
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}
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/* Generate output. We generate 228 bits of
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* keystream output. The first 114 bits is for
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* the A->B frame; the next 114 bits is for the
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* B->A frame. You allocate a 15-byte buffer
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* for each direction, and this function fills
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* it in. */
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void run(byte AtoBkeystream[], byte BtoAkeystream[]) {
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int i;
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/* Zero out the output buffers. */
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for (i = 0; i <= 113 / 8; i++)
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AtoBkeystream[i] = BtoAkeystream[i] = 0;
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/* Generate 114 bits of keystream for the
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* A->B direction. Store it, MSB first. */
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for (i = 0; i < 114; i++) {
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clock(0, 0);
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AtoBkeystream[i/8] |= getbit() << (7 - (i & 7));
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}
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/* Generate 114 bits of keystream for the
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* B->A direction. Store it, MSB first. */
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for (i = 0; i < 114; i++) {
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clock(0, 0);
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BtoAkeystream[i/8] |= getbit() << (7 - (i & 7));
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}
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}
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void runA51(byte AtoBkeystream[], byte BtoAkeystream[]) {
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int i;
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/* Zero out the output buffers. */
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for (i = 0; i < 114; i++){
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AtoBkeystream[i] = 0;
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}
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/* Generate 114 bits of keystream for the
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* A->B direction. Store it, MSB first. */
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for (i = 0; i < 114; i++) {
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clock(0, 0);
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AtoBkeystream[i] = getbit();
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}
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/* Generate 114 bits of keystream for the
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* B->A direction. Store it, MSB first. */
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for (i = 0; i < 114; i++) {
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clock(0, 0);
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BtoAkeystream[i] = getbit();
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}
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}
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#endif /* A5_1_2_H */
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@ -26,8 +26,10 @@
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#include <grgsm/gsmtap.h>
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#include <grgsm/endian.h>
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#include "decryption_impl.h"
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#include "a5_1_2.h"
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extern "C" {
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#include <osmocom/gsm/a5.h>
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}
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const uint32_t BURST_SIZE=148;
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@ -66,14 +68,24 @@ namespace gr {
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void decryption_impl::set_k_c(const std::vector<uint8_t> & k_c)
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{
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d_k_c = k_c;
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if (k_c.size() == 8)
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{
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for (int i=0; i<8; i++)
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{
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d_k_c[i] = k_c[i];
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}
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}
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else
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{
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for (int i=0; i<8; i++)
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{
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d_k_c[i] = 0;
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}
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}
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}
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void decryption_impl::decrypt(pmt::pmt_t msg)
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{
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if(d_k_c.size() != 8){
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message_port_pub(pmt::mp("bursts"), msg);
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} else
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if(d_k_c[0] == 0 && d_k_c[1] == 0 && d_k_c[2] == 0 && d_k_c[3] == 0 &
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d_k_c[4] == 0 && d_k_c[5] == 0 && d_k_c[6] == 0 && d_k_c[7] == 0)
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{
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|
@ -81,9 +93,7 @@ namespace gr {
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} else
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{
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uint8_t decrypted_data[BURST_SIZE];
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uint8_t AtoBkeystream[114];
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uint8_t BtoAkeystream[114];
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uint8_t * keystream;
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uint8_t keystream[114];
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pmt::pmt_t header_plus_burst = pmt::cdr(msg);
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gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst);
|
||||
|
@ -91,19 +101,13 @@ namespace gr {
|
|||
|
||||
uint32_t frame_number = be32toh(header->frame_number);
|
||||
bool uplink_burst = (be16toh(header->arfcn) & 0x4000) ? true : false;
|
||||
uint32_t t1 = frame_number / (26*51);
|
||||
uint32_t t2 = frame_number % 26;
|
||||
uint32_t t3 = frame_number % 51;
|
||||
uint32_t frame_number_mod = (t1 << 11) + (t3 << 5) + t2;
|
||||
keysetup(&d_k_c[0], frame_number_mod);
|
||||
runA51(AtoBkeystream, BtoAkeystream);
|
||||
|
||||
if(uplink_burst){
|
||||
//process uplink burst
|
||||
keystream = BtoAkeystream;
|
||||
osmo_a5(1, d_k_c, frame_number, NULL, keystream);
|
||||
} else {
|
||||
//process downlink burst
|
||||
keystream = AtoBkeystream;
|
||||
osmo_a5(1, d_k_c, frame_number, keystream, NULL);
|
||||
}
|
||||
/* guard bits */
|
||||
for (int i = 0; i < 3; i++) {
|
||||
|
|
|
@ -1,17 +1,17 @@
|
|||
/* -*- c++ -*- */
|
||||
/*
|
||||
/*
|
||||
* Copyright 2014 <+YOU OR YOUR COMPANY+>.
|
||||
*
|
||||
*
|
||||
* This is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License as published by
|
||||
* the Free Software Foundation; either version 3, or (at your option)
|
||||
* any later version.
|
||||
*
|
||||
*
|
||||
* This software is distributed in the hope that it will be useful,
|
||||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
* GNU General Public License for more details.
|
||||
*
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this software; see the file COPYING. If not, write to
|
||||
* the Free Software Foundation, Inc., 51 Franklin Street,
|
||||
|
@ -30,7 +30,8 @@ namespace gr {
|
|||
class decryption_impl : public decryption
|
||||
{
|
||||
private:
|
||||
std::vector<uint8_t> d_k_c;
|
||||
// std::vector<uint8_t> d_k_c;
|
||||
uint8_t d_k_c[8];
|
||||
void decrypt(pmt::pmt_t msg);
|
||||
public:
|
||||
decryption_impl(const std::vector<uint8_t> & k_c);
|
||||
|
|
Loading…
Reference in New Issue