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DMR: Correct KS Offset Application on Chained P_Head;

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lwvmobile
2025-03-03 22:58:52 -05:00
parent 5fcfb141a6
commit 4255a2f9ba
1 changed files with 5 additions and 5 deletions
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10
src/dmr_block.c
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@@ -378,7 +378,7 @@ void dmr_dheader (dsd_opts * opts, dsd_state * state, uint8_t dheader[], uint8_t
//a second extended header, and the keystream on that starts after the sap/dpf and mfid value
//this is the only time starting the keystream at an offset value will be required
//set ks start value to 3 (testing based on only example I have, need more samples)
//set ks start value to 3 (confirmed on several samples of various enc ciphers)
state->data_ks_start[slot] = 3;
}
@@ -892,8 +892,8 @@ void dmr_block_assembler (dsd_opts * opts, dsd_state * state, uint8_t block_byte
{
// decrypted_pdu = 0; //hasn't been decrypted yet
int poc = (int)state->data_block_poc[slot]; //say that three times real fast
int end = ((blocks+1)*block_len)-4-poc;
int start = (int)state->data_ks_start[slot];
int end = ((blocks+1)*block_len)-4-poc-start;
//sanity check on end, has to be a positive value
if (end < 0) end = 3096; //its a signed interger, so should reflect negative values here and not rollover
int alg = 0;
@@ -957,8 +957,8 @@ void dmr_block_assembler (dsd_opts * opts, dsd_state * state, uint8_t block_byte
//will want to rework output_blocks to be a pointer instead of a fixed size (done)
if (alg == 1 && R != 0)
{
for (i = start; i < end; i++)
state->dmr_pdu_sf[slot][i] ^= ob[i%3096];
for (i = 0; i < end; i++)
state->dmr_pdu_sf[slot][i+start] ^= ob[i%3096];
}
//BP key application
else if (alg == 0) //&& state->K != 0
@@ -980,7 +980,7 @@ void dmr_block_assembler (dsd_opts * opts, dsd_state * state, uint8_t block_byte
if (bp_key != 0)
{
for (i = start; i < end; i++)
for (i = start; i < (end-start); i++)
state->dmr_pdu_sf[slot][i] ^= ob[i%2]; //modulus 2 here, just rinse and repeat
decrypted_pdu = 1;