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Decode encrypted POCSAG messages (thanks to JG1UAA for the code).

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This commit is contained in:
Jonathan Naylor 2020-12-14 12:22:43 +00:00
parent 56f361b3e4
commit 77daf86723
2 changed files with 24 additions and 3 deletions
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23
POCSAGControl.cpp
View file

@ -1,5 +1,5 @@
/*
* Copyright (C) 2018,2019 Jonathan Naylor, G4KLX
* Copyright (C) 2018,2019,2020 Jonathan Naylor, G4KLX
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -147,10 +147,23 @@ bool CPOCSAGControl::readNetwork()
addAddress(functional, output->m_ric, output->m_buffer);
std::string out;
switch (functional) {
case FUNCTIONAL_ALPHANUMERIC:
output->m_text = std::string((char*)(data + 4U), length - 4U);
LogDebug("Message to %07u, func Alphanumeric: \"%s\"", output->m_ric, output->m_text.c_str());
switch (output->m_ric) {
case 4512U:
decodeROT1(output->m_text, 3U, out);
LogDebug("Message to %07u, func Alphanumeric: (%u) \"%s\"", output->m_ric, output->m_text.at(1U) - 0x1FU, out.c_str());
break;
case 4520U:
decodeROT1(output->m_text, 2U, out);
LogDebug("Message to %07u, func Alphanumeric: (%u-%u) \"%s\"", output->m_ric, output->m_text.at(0U) - 0x1FU, output->m_text.at(1U) - 0x20U, out.c_str());
break;
default:
LogDebug("Message to %07u, func Alphanumeric: \"%s\"", output->m_ric, output->m_text.c_str());
break;
}
packASCII(output->m_text, output->m_buffer);
break;
case FUNCTIONAL_NUMERIC:
@ -483,3 +496,9 @@ void CPOCSAGControl::enable(bool enabled)
m_enabled = enabled;
}
void CPOCSAGControl::decodeROT1(const std::string& in, unsigned int start, std::string& out) const
{
for (size_t i = start; i < in.length(); i++)
out += in.at(i) - 1U;
}

4
POCSAGControl.h
View file

@ -1,5 +1,5 @@
/*
* Copyright (C) 2018,2019 by Jonathan Naylor G4KLX
* Copyright (C) 2018,2019,2020 by Jonathan Naylor G4KLX
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -81,6 +81,8 @@ private:
bool openFile();
bool writeFile(const unsigned char* data);
void closeFile();
void decodeROT1(const std::string& in, unsigned int start, std::string& out) const;
};
#endif