[PATCH 3/3] Add A5/3 support.

[Max Suraev]

---
 src/gsm/a5.c |   43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/gsm/a5.c b/src/gsm/a5.c
index 93b22c7..5815aa7 100644
--- a/src/gsm/a5.c
+++ b/src/gsm/a5.c
@@ -39,6 +39,7 @@
 #include <string.h>
 #include <osmocom/core/bits.h>
 #include <osmocom/gsm/a5.h>
+#include <osmocom/gsm/kasumi.h>
 
 /*! \brief Main method to generate a A5/x cipher stream
  *  \param[in] n Which A5/x method to use
@@ -71,6 +72,10 @@ osmo_a5(int n, const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul)
 		osmo_a5_2(key, fn, dl, ul);
 		break;
 
+	case 3:
+		osmo_a5_3(key, fn, dl, ul);
+		break;
+
 	default:
 		/* a5/[4..7] not supported here/yet */
 		return -ENOTSUP;
@@ -368,4 +373,42 @@ osmo_a5_2(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul)
 	}
 }
 
+/* ------------------------------------------------------------------------ */
+/* A5/3                                                                     */
+/* ------------------------------------------------------------------------ */
+
+/*! \brief Generate a GSM A5/3 cipher stream
+ *  \param[in] key 8 byte array for the key (as received from the SIM)
+ *  \param[in] fn Frame number
+ *  \param[out] dl Pointer to array of ubits to return Downlink cipher stream
+ *  \param[out] ul Pointer to array of ubits to return Uplink cipher stream
+ *
+ * Either (or both) of dl/ul should be NULL if not needed.
+ *
+ * Implementation based on specifications from 3GPP TS 55.216, 3GPP TR 55.919 and ETSI TS 135 202
+ * with slight simplifications (CE hardcoded to 0).
+ */
+void
+osmo_a5_3(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul)
+{
+    /* internal function require 128 bit key so we expand by concatenating supplied 64 bit key */
+    uint8_t i, ck[16], gamma[32], _key[8];
+    memcpy(_key, key, 8);
+    osmo_revbytes_buf(_key, 8); /* reverse key byte order to match the way it's stored in SIM */
+    memcpy(ck, _key, 8);
+    memcpy(ck + 8, _key, 8);
+
+    uint32_t fn_count = osmo_a5_fn_count(fn); /* Frame count load */
+    if (dl) {
+	kgcore(0xF, 0, fn_count, 0, ck, gamma, 114);
+	osmo_pbit2ubit(dl, gamma, 114);
+    }
+    if (ul) {
+	kgcore(0xF, 0, fn_count, 0, ck, gamma, 228);
+	uint8_t uplink[15];
+	for(i = 0; i < 15; i++) uplink[i] = (gamma[i + 14] << 2) + (gamma[i + 15] >> 6);
+	osmo_pbit2ubit(ul, uplink, 114);
+    }
+}
+
 /*! @} */
-- 
1.7.10.4


--------------000004050908040808070403--