Diff: LoRaMacCrypto.cpp

Branch:

class_b

Revision:

38:182ba91524e4

Parent:

2:14a5d6ad92d5

--- a/LoRaMacCrypto.cpp	Tue Aug 08 19:27:17 2017 -0400
+++ b/LoRaMacCrypto.cpp	Wed Aug 09 16:20:21 2017 -0400
@@ -15,7 +15,7 @@
 
 License: Revised BSD License, see LICENSE.TXT file include in the project
 
-Maintainer: Miguel Luis ( Semtech ), Gregory Cristian ( Semtech ) and Daniel Jäckle ( STACKFORCE )
+Maintainer: Miguel Luis ( Semtech ), Gregory Cristian ( Semtech ) and Daniel Jaeckle ( STACKFORCE )
 */
 #include <stdlib.h>
 #include <stdint.h>
@@ -200,3 +200,37 @@
     memcpy1( nonce + 7, pDevNonce, 2 );
     aes_encrypt( nonce, appSKey, &AesContext );
 }
+
+void LoRaMacBeaconComputePingOffset( uint64_t beaconTime, uint32_t address, uint16_t pingPeriod, uint16_t *pingOffset )
+{
+    uint8_t zeroKey[16];
+    uint8_t buffer[16];
+    uint8_t cipher[16];
+    uint32_t result = 0;
+    /* Refer to chapter 15.2 of the LoRaWAN specification v1.1. The beacon time
+     * GPS time in seconds modulo 2^32
+     */
+    uint32_t time = ( beaconTime % ( ( ( uint64_t ) 1 ) << 32 ) );
+
+    memset1( zeroKey, 0, 16 );
+    memset1( buffer, 0, 16 );
+    memset1( cipher, 0, 16 );
+    memset1( AesContext.ksch, '\0', 240 );
+
+    buffer[0] = ( time ) & 0xFF;
+    buffer[1] = ( time >> 8 ) & 0xFF;
+    buffer[2] = ( time >> 16 ) & 0xFF;
+    buffer[3] = ( time >> 24 ) & 0xFF;
+
+    buffer[4] = ( address ) & 0xFF;
+    buffer[5] = ( address >> 8 ) & 0xFF;
+    buffer[6] = ( address >> 16 ) & 0xFF;
+    buffer[7] = ( address >> 24 ) & 0xFF;
+
+    aes_set_key( zeroKey, 16, &AesContext );
+    aes_encrypt( buffer, cipher, &AesContext );
+
+    result = ( ( ( uint32_t ) cipher[0] ) + ( ( ( uint32_t ) cipher[1] ) * 256 ) );
+
+    *pingOffset = ( uint16_t )( result % pingPeriod );
+}