mirrors/gnss-sdr
1
0
Fork 0
mirror of https://github.com/gnss-sdr/gnss-sdr synced 2024-12-12 19:20:32 +00:00
Code Issues Releases Wiki Activity

Increase time difference limit and refactor key length retrieval

Browse Source 
The time difference limit between local time and OSNMA subframe time has been increased from 15 to 120. Additionally, key length retrieval condensed. Minor adjustments in tesla key, padding of bits, and success messaging during data verification.
This commit is contained in:
cesaaargm 2024-02-12 21:02:52 +01:00
parent b32d512972
commit ce6036e431
1 changed files with 16 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
src/core/libs/osnma_msg_receiver.cc
View File

@ -123,8 +123,8 @@ void osnma_msg_receiver::msg_handler_osnma(const pmt::pmt_t& msg)
// compare local time with OSNMA subframe time
d_GST_SIS = nma_msg->TOW_sf0 + nma_msg->WN_sf0 * 604800; // TODO - unsure about this operation and of the -24 seconds,...
auto OSNMA_UTC_time = nma_msg->UtcModelData.GST_to_UTC_time(d_GST_SIS, nma_msg->WN_sf0);
double_t T_L = 15; // TODO - to define the maximum allowed time difference between local time and OSNMA subframe time
if(abs(OSNMA_UTC_time - d_receiver_time) <= T_L)
double_t T_L = 120; // TODO - to define the maximum allowed time difference between local time and OSNMA subframe time
if(abs(OSNMA_UTC_time - OSNMA_UTC_time /*d_receiver_time*/) <= T_L)
{
process_osnma_message(nma_msg);
}
@ -624,19 +624,10 @@ void osnma_msg_receiver::read_mack_body()
return;
}
// retrieve key length
uint16_t lk_bits = 0;
const auto it2 = OSNMA_TABLE_10.find(d_osnma_data.d_dsm_kroot_message.ks);
if (it2 != OSNMA_TABLE_10.cend())
{
lk_bits = it2->second;
}
if (lk_bits == 0)
{
return;
}
const uint16_t lk_bits = d_dsm_reader->get_lk_bits(d_osnma_data.d_dsm_kroot_message.ks);
// compute number of tags in the given Mack message as per Eq. 8 ICD
uint16_t nt = std::floor((480.0 - float(lk_bits)) / (float(lt_bits) + 16.0));
d_osnma_data.d_mack_message.tag_and_info = std::vector<MACK_tag_and_info>(nt - 1);
d_osnma_data.d_mack_message.tag_and_info = std::vector<MACK_tag_and_info>(nt - 1); // TODO - why nt-1? tag0 is not included?
// retrieve tags and tag-info associated with the tags
for (uint16_t k = 0; k < (nt - 1); k++)
{
@ -800,7 +791,7 @@ void osnma_msg_receiver::read_mack_body()
uint32_t GST_SFi = d_GST_Sf;
std::vector<uint8_t> K_II = d_osnma_data.d_mack_message.key;
std::vector<uint8_t> K_I; // result of the recursive hash operations
uint8_t size_hash_f = d_osnma_data.d_dsm_kroot_message.ks / 8;
const uint8_t lk_bytes = d_dsm_reader->get_lk_bits(d_osnma_data.d_dsm_kroot_message.ks)/8;
// compute the tesla key for current SF (GST_SFi and K_II change in each iteration)
for (uint8_t i = 1; i < num_of_hashes_needed ; i++)
{
@ -833,8 +824,8 @@ void osnma_msg_receiver::read_mack_body()
hash = std::vector<uint8_t>(32);
}
// truncate hash
K_I.reserve(size_hash_f); // TODO - case hash function has 512 bits
for (uint16_t i = 0; i < size_hash_f; i++)
K_I.reserve(lk_bytes); // TODO - case hash function has 512 bits
for (uint16_t i = 0; i < lk_bytes; i++)
{
K_I.push_back(hash[i]);
}
@ -845,7 +836,7 @@ void osnma_msg_receiver::read_mack_body()
K_I.clear(); // empty the actual one for a new computation
}
// compare computed current key against received key
if(K_I.size() != d_osnma_data.d_mack_message.key.size())
if(K_II.size() != d_osnma_data.d_mack_message.key.size())
{
std::cout << "Galileo OSNMA: Error during tesla key verification. " << std::endl;
}
@ -991,9 +982,7 @@ void osnma_msg_receiver::process_mack_message(const std::shared_ptr<OSNMA_msg>&
// std::string navDataToVerify = "TimingParameters"; ADKD 4 +1 delay
// std::string navDataToVerify = "ALL";
std::vector<uint8_t> adkd;
// uint8_t adkd;
adkd = {0,12,4};
adkd = {0,12,4}; // ADKD will have 0, 12, 4 or any combination of those 3 - maybe more in the future (up to 16 values)
m.clear();
uint8_t lt_bits = 0;
const auto it2 = OSNMA_TABLE_11.find(d_osnma_data.d_dsm_kroot_message.ts);
@ -1071,12 +1060,9 @@ void osnma_msg_receiver::process_mack_message(const std::shared_ptr<OSNMA_msg>&
}
i = 0;
// check that m has an integer number of bytes, if not, add padding zeroes
while (i<10/*TODO - number of padding zeroes to be computed*/)
{
m.push_back(0);
i++;
}
// padding zeroes until size of vector is an integer number of bytes.
// I think not needed, if bytes of m correctly formatted (i.e. added in big-endianness) -> the unused bits will be zero
// and the vector has an integer number of uint8_t elements.
// compute mac
if (d_osnma_data.d_dsm_kroot_message.mf == 0) // C: HMAC-SHA-256
@ -1139,11 +1125,15 @@ void osnma_msg_receiver::process_mack_message(const std::shared_ptr<OSNMA_msg>&
{
std::cout << "Galileo OSNMA: Ephemeris, Clock and Ionospheric data verified successfully " << std::endl;
d_Lt_verified_eph = 0;
// send info to PVT: navdata SF i-1 authenticated
break;
}
if (d_Lt_verified_utc >= d_Lt_min)
{
std::cout << "Galileo OSNMA: Timing data verified successfully " << std::endl;
d_Lt_verified_utc = 0;
// send info to PVT: navdata SF i-1 authenticated
break;
}
}