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I have c++ code that read 16 byte from a file as char value
And I have a table of unsigned char from 0 to 255
I want to use byte values from file as a index in my unsigned char table to change the original file byte values but I get negative value from file and as you know you can't use negative value as a index in array
What should I do ?
Edit
const unsigned char TopSbox[256] = {
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};
void RunFunction(){
ifstream reader;
ofstream writer;
reader.open(myfile_address, ifstream::binary);
writer.open(storage_file,ofstream::out);
unsigned int BufferSize =16;
char *Transform_Buffer = new char[BufferSize];
reader.read(Transform_Buffer, BufferSize);
ExchangeData(Transform_Buffer, BufferSize);
writer.write(Transform_Buffer, BufferSize);
writer.flush();
}
void EData::ExchangeData(char data[], const unsigned int size){
for (unsigned int i = 0; i<size; i++){
data[i] = TopSbox[data[i]];
}
}
Don't use operator new unless absolutely necessary.
Rather than
char *Transform_Buffer = new char[BufferSize];
you can define the buffer as a local array:
const unsigned int BufferSize = 16;
unsigned char Transform_Buffer[BufferSize];
For this to work, you should declare BufferSize as const. Notice also that I declared the elements of the buffer as unsigned char.
Then, this line
reader.read(Transform_Buffer, BufferSize);
can be replaced with
reader.read(reinterpret_cast<char*>(Transform_Buffer), BufferSize);
and similarly for writer.
Please also replace all char* in function declarations with unsigned char*, eg:
void EData::ExchangeData(unsigned char data[], const unsigned int size){
I guess everything should work as expected now.
Just have buffer of unsigned chars. Then pass it as char* to ifstream::read. Let's say char* works kind of like a generic pointer.
You may want to prefer to use standard containers.
std::vector<unsigned char> transform_buffer(buffer_size);
reader.read(static_cast<char*>(transform_buffer.data()), transform_buffer.size());
exchange_data(transform_buffer);
}
void exchange_data(std::vector<unsigned char>& transform_buffer) {
for (auto&& i : transform_buffer) {
i = TopSbox[i];
}
}
As part of a project I'm working on with pulling data from a bluetooth device, I was provided a CRC8 function from the manufacturer to use. I'm writing the application in Swift, but the function they provided is in C++.
Below is the function they've provided in C++
unsigned char xTable_CRC8[]={0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5,0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2,0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC,0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C,0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B,0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB,0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB,0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 };
uint8_t CRC8(char *RP_ByteData, unsigned int Buffer_Size) {
uint8_t x,R_CRC_Data;
R_CRC_Data=0;
for(unsigned int i = 0; i < Buffer_Size; i++) {
x = R_CRC_Data ^ (*RP_ByteData);
R_CRC_Data = xTable_CRC8[x];
RP_ByteData++;
}
return R_CRC_Data;
}
Here is my attempt at converting it so far:
func calCR8(buf : [UInt8]) -> UInt8 {
let initialValue : UInt8 = UInt8.min;
let Table_CRC8 : [UInt8] = [
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15,0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,
0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,
0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,
0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,
0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,
0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,
0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,
0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,
0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,
0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C,0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,
0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B,0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,
0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,
0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB,0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 ];
var crc = initialValue;
let x: UInt8
for i in 0 ..< buf.count{
x = crc ^ buf
crc = Table_CRC8[x]
}
return crc;
}
}
I'm dealing with two type errors: Cannot convert value of type '[UInt8]' to expected argument type 'UInt8', and Cannot convert value of type 'UInt8' to expected argument type 'Int'. I feel very lost and uncomfortable here.
Basically, this function will be called in a manner as such:
var buf : [UInt8] = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];
buf[0] = 0xAA;
buf[1] = 0x14;
buf[2] = ~0x14
buf[buf.count - 1] = self.calcCR8(buf)
Based on this byte array being use a parameter for this example, I'm expecting to get 0xC6 returned.
You have a few small mistakes. First, you are trying to perform the xor calculation on buf - this is the entire array; You need to access a single element buf[i].
Your second issue is that you can't index a sequence with a UInt8, so you need to make an Int equivalent in order to access the Table_CRC8 array.
Finally you are declaring x as a let (constant) outside the for loop, so you can't change it. You can move the declaration of x inside the for loop to address this.
Making these small changes will give you code that compiles:
for i in 0 ..< buf.count {
let x = crc ^ buf[i]
crc = Table_CRC8[Int(x)]
}
You can make it more 'Swifty' by changing the name of the CRC table to conform to Swift idioms and use an iteration loop rather than a for in <range> loop:
func calcCRC8(_ buf : [UInt8]) -> UInt8 {
let tableCRC8 : [UInt8] = [
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15,0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,
0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,
0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,
0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,
0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,
0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,
0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,
0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,
0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,
0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C,0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,
0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B,0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,
0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,
0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB,0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 ];
var crc = UInt8.min
for byte in buf {
let x = crc ^ byte
crc = tableCRC8[Int(x)]
}
return crc
}
I have a weird issue while creating a substitution for AES encryption.
I use a lookup table, named SBox, to substitute the bytes in the string state (technically a vector, but it's irrelevant)
const vector<byte> SBox =
{
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};
void subBytes(vector<string>& state)
{
for (int i=0; i<4; ++i)
{
for (int j=0; j<4; ++j)
{
state[i][j] = SBox[state[i][j]];
}
}
}
this does not work but if I use
state[i][j] = SBox[state[i][j]&0xff];
then everything magically works again. I thought a char was byte-sized, so AND'ing by 0xff had no influence. FYI I am running under 64-bit machine. This is a little bit annoying as I have to use a lot of lines like that in other functions. Can anybody explain why? Is there another solution?
state[i][j] may return signed chars so if your character codes are larger than 7bits you are using negative index to SBox[state[i][j]]
Another thing:
if you have fix sizes for SBox and states: why not using std::array instead of vector?
std::array<byte,256> for SBox
and std::array<std::array<char,4>,4> for State.
Also you may use the size member of your vectors or arrays instead using magic number in your loop.
I have to translale some code into python. Both are to be 32 bits. How do I verify that?
const char kEncryptionKey[] = {
0xb0, 0x8c, 0x70, 0xcf, 0xbc, 0xb0, 0xeb, 0x6c, 0xab, 0x7e, 0x82, 0xc6,
0xb7, 0x5d, 0xa5, 0x20, 0x72, 0xae, 0x62, 0xb2, 0xbf, 0x4b, 0x99, 0x0b,
0xb8, 0x0a, 0x48, 0xd8, 0x14, 0x1e, 0xec, 0x07
};
const char kIntegrityKey[] = {
0xbf, 0x77, 0xec, 0x55, 0xc3, 0x01, 0x30, 0xc1, 0xd8, 0xcd, 0x18, 0x62,
0xed, 0x2a, 0x4c, 0xd2, 0xc7, 0x6a, 0xc3, 0x3b, 0xc0, 0xc4, 0xce, 0x8a,
0x3d, 0x3b, 0xbd, 0x3a, 0xd5, 0x68, 0x77, 0x92
};
So..in python:
kIntegrityKey = ????
kEncryptionKey = ????
You could store your hexadecimal numbers in a list:
kIntegrityKey = [0xbf, 0x77, 0xec, 0x55, 0xc3, 0x01, 0x30, 0xc1, 0xd8, 0xcd, 0x18, 0x62,
0xed, 0x2a, 0x4c, 0xd2, 0xc7, 0x6a, 0xc3, 0x3b, 0xc0, 0xc4, 0xce, 0x8a,
0x3d, 0x3b, 0xbd, 0x3a, 0xd5, 0x68, 0x77, 0x92]
and the same thing to kEncryptionKey.
Update: If you have concerns related to the size of your data, you could pack your data into an array. For example:
>>> import array
>>> kIntegrityKey = array.array('B', [0xbf, 0x77, 0xec, 0x55, 0xc3, 0x01, 0x30, 0xc1,
... 0xd8, 0xcd, 0x18, 0x62, 0xed, 0x2a, 0x4c, 0xd2, 0xc7, 0x6a, 0xc3, 0x3b, 0xc0, 0xc4,
... 0xce, 0x8a, 0x3d, 0x3b, 0xbd, 0x3a, 0xd5, 0x68, 0x77, 0x92])
>>> len(kIntegrityKey)
32
>>> kIntegrityKey.itemsize
1
The first argument to array ('B') indicates that we want to store the second parameter (your unsigned char list) using a list of unisgned char.
The itemsize attribute is described in the docstring as:
itemsize -- the length in bytes of one array item
Python strings can be given arbitrary hex characters using the \x special character.
kIntegrityKey = "\xb0\x8c\x70\xcf ..."
Py3k has a "bytes" type which is likely ideal for this application.
NB: python 2 has a bytes type now too, but it's just an alias of str.
I am using Crypto++ for the first time, and I am having some trouble. Why does this work in C# (with the same keys), but not with Crypto++? I will show my C# and C++ code below.
C# code (this works!):
byte[] Modulus = new byte[] { 0xA3, 0x1D, 0x6C, 0xE5, 0xFA, 0x95, 0xFD, 0xE8, 0x90, 0x21, 0xFA, 0xD1, 0x0C, 0x64, 0x19, 0x2B, 0x86, 0x58, 0x9B, 0x17, 0x2B, 0x10, 0x05, 0xB8, 0xD1, 0xF8, 0x4C, 0xEF, 0x53, 0x4C, 0xD5, 0x4E, 0x5C, 0xAE, 0x86, 0xEF, 0x92, 0x7B, 0x90, 0xD1, 0xE0, 0x62, 0xFD, 0x7C, 0x54, 0x55, 0x9E, 0xE0, 0xE7, 0xBE, 0xFA, 0x3F, 0x9E, 0x15, 0x6F, 0x6C, 0x38, 0x4E, 0xAF, 0x07, 0x0C, 0x61, 0xAB, 0x51, 0x5E, 0x23, 0x53, 0x14, 0x18, 0x88, 0xCB, 0x6F, 0xCB, 0xC5, 0xD6, 0x30, 0xF4, 0x06, 0xED, 0x24, 0x23, 0xEF, 0x25, 0x6D, 0x00, 0x91, 0x77, 0x24, 0x9B, 0xE5, 0xA3, 0xC0, 0x27, 0x90, 0xC2, 0x97, 0xF7, 0x74, 0x9D, 0x6F, 0x17, 0x83, 0x7E, 0xB5, 0x37, 0xDE, 0x51, 0xE8, 0xD7, 0x1C, 0xE1, 0x56, 0xD9, 0x56, 0xC8, 0xC3, 0xC3, 0x20, 0x9D, 0x64, 0xC3, 0x2F, 0x8C, 0x91, 0x92, 0x30, 0x6F, 0xDB };
byte[] Exponent = new byte[] { 0x00, 0x01, 0x00, 0x01 };
byte[] P = new byte[] { 0xCC, 0xE7, 0x5D, 0xFE, 0x72, 0xB6, 0xFD, 0xE7, 0x1D, 0xE3, 0x1A, 0x0E, 0xAC, 0x33, 0x7A, 0xB9, 0x21, 0xE8, 0x8A, 0x84, 0x9B, 0xDA, 0x9F, 0x1E, 0x58, 0x34, 0x68, 0x7A, 0xB1, 0x1D, 0x7E, 0x1C, 0x18, 0x52, 0x65, 0x7B, 0x97, 0x8E, 0xA7, 0x6A, 0x9D, 0xEE, 0x5A, 0x77, 0x52, 0x3B, 0x71, 0x8F, 0x33, 0xD0, 0x49, 0x5E, 0xC3, 0x30, 0x39, 0x72, 0x36, 0xBF, 0x1D, 0xD9, 0xF2, 0x24, 0xE8, 0x71 };
byte[] Q = new byte[] { 0xCB, 0xCA, 0x58, 0x74, 0xD4, 0x03, 0x62, 0x93, 0x06, 0x50, 0x1F, 0x42, 0xF6, 0xAA, 0x59, 0x36, 0xA7, 0xA1, 0xF3, 0x97, 0x5C, 0x9A, 0xC8, 0x6A, 0x27, 0xCF, 0x85, 0x05, 0x2A, 0x66, 0x41, 0x6A, 0x7F, 0x2F, 0x84, 0xC8, 0x18, 0x13, 0xC6, 0x1D, 0x8D, 0xC7, 0x32, 0x2F, 0x72, 0x19, 0x3F, 0xA4, 0xED, 0x71, 0xE7, 0x61, 0xC0, 0xCF, 0x61, 0xAE, 0x8B, 0xA0, 0x68, 0xA7, 0x7D, 0x83, 0x23, 0x0B };
byte[] DP = new byte[] { 0x4C, 0xCA, 0x74, 0xE6, 0x74, 0x35, 0x72, 0x48, 0x58, 0x62, 0x11, 0x14, 0xE8, 0xA2, 0x4E, 0x5E, 0xED, 0x7F, 0x49, 0xD2, 0x52, 0xDA, 0x87, 0x01, 0x87, 0x4A, 0xF4, 0xD0, 0xEE, 0x69, 0xC0, 0x26, 0x65, 0x53, 0x13, 0xE7, 0x52, 0xB0, 0x4A, 0xBB, 0xE1, 0x3E, 0x3F, 0xB7, 0x32, 0x21, 0x46, 0xF8, 0xC5, 0x11, 0x4D, 0x3D, 0xEF, 0x66, 0xB6, 0x50, 0xC0, 0x85, 0xB5, 0x79, 0x45, 0x8F, 0x61, 0x71 };
byte[] InverseQ = new byte[] { 0x28, 0x6A, 0xBB, 0xD1, 0x93, 0x95, 0x94, 0x1A, 0x6E, 0xED, 0xD7, 0x0E, 0xC0, 0x61, 0x2B, 0xC2, 0xEF, 0xE1, 0x86, 0x3D, 0x34, 0x12, 0x88, 0x6F, 0x94, 0xA4, 0x48, 0x6E, 0xC9, 0x87, 0x1E, 0x46, 0x00, 0x46, 0x00, 0x52, 0x8E, 0x9F, 0x47, 0xC0, 0x8C, 0xAB, 0xBC, 0x49, 0xAC, 0x5B, 0x13, 0xF2, 0xEC, 0x27, 0x8D, 0x1B, 0x6E, 0x51, 0x06, 0xA6, 0xF1, 0x62, 0x1A, 0xEB, 0x78, 0x2E, 0x88, 0x48 };
byte[] D = new byte[] { 0x9B, 0xF9, 0xDE, 0xC2, 0x45, 0x93, 0x4C, 0x4C, 0xAC, 0x48, 0x2B, 0xA8, 0x4D, 0xFC, 0xD7, 0xED, 0xB2, 0xFB, 0x72, 0xE9, 0xEA, 0xC1, 0x88, 0x39, 0x07, 0x2A, 0x6F, 0x34, 0x07, 0x81, 0x97, 0x7E, 0xCD, 0xFA, 0x21, 0x02, 0xF5, 0xDD, 0x30, 0xDD, 0x22, 0x4A, 0xB3, 0x41, 0xE5, 0x89, 0x80, 0x73, 0xC4, 0xAF, 0x90, 0x9E, 0x2B, 0x50, 0x8A, 0x0A, 0xD4, 0x6E, 0xBD, 0x0F, 0x15, 0x79, 0x37, 0x95, 0xE8, 0x3D, 0xCF, 0x4C, 0x6D, 0xFF, 0x51, 0x65, 0xE7, 0x90, 0xC1, 0xAC, 0x2D, 0xC6, 0xEB, 0x47, 0x19, 0x2D, 0xD0, 0x58, 0x74, 0x79, 0xAC, 0x08, 0x1C, 0xA3, 0x1D, 0xD0, 0xCE, 0x39, 0x2E, 0xC3, 0xFA, 0x66, 0xEF, 0xC7, 0x8E, 0x10, 0x2F, 0xE4, 0xA1, 0xE7, 0x4E, 0xA8, 0x42, 0xF0, 0xF4, 0xFD, 0x10, 0xA6, 0x67, 0x64, 0xCB, 0x3A, 0x6D, 0x4D, 0x51, 0xEC, 0x1F, 0x9D, 0x56, 0x26, 0xC2, 0xFC };
byte[] DQ = new byte[] { 0xAF, 0xDC, 0x46, 0xE7, 0x52, 0x8A, 0x35, 0x47, 0xA1, 0x1C, 0x05, 0x4E, 0x39, 0x24, 0x99, 0xE6, 0x43, 0x54, 0xCB, 0xAB, 0xE3, 0xDB, 0x22, 0x76, 0x11, 0x32, 0xD0, 0x9C, 0xBB, 0x91, 0x10, 0x84, 0x81, 0x8B, 0x15, 0x2F, 0xC3, 0x2F, 0x55, 0x38, 0xED, 0xBF, 0x67, 0x3C, 0x70, 0x5E, 0xFF, 0x80, 0x28, 0xF3, 0xB1, 0x73, 0xB6, 0xFA, 0x7F, 0x56, 0x2B, 0xE1, 0xDA, 0x4E, 0x27, 0x4E, 0xC2, 0x2F };
RSAParameters rsaParams = new RSAParameters();
rsaParams.Modulus = Modulus;
rsaParams.Exponent = Exponent;
rsaParams.P = P;
rsaParams.Q = Q;
rsaParams.DP = DP;
rsaParams.InverseQ = InverseQ;
rsaParams.D = D;
rsaParams.DQ = DQ;
RSACryptoServiceProvider crypt = new RSACryptoServiceProvider();
crypt.ImportParameters(rsaParams);
RSAPKCS1SignatureFormatter formatter = new RSAPKCS1SignatureFormatter();
formatter.SetHashAlgorithm("SHA1");
formatter.SetKey(crypt);
byte[] dataFile = new byte[] { 0x6F, 0x9F, 0x07, 0x04, 0xE2, 0x1A, 0xF7, 0xB8, 0xB2, 0x4F, 0x8D, 0x66, 0x49, 0xA1, 0x09, 0xA7, 0xB2, 0x22, 0x3C, 0xF9};
byte[] signature = formatter.CreateSignature(dataFile);
Now, my C++ code, which doesn't work:
const char ModulusCON[0x80] = { 0xA3, 0x1D, 0x6C, 0xE5, 0xFA, 0x95, 0xFD, 0xE8, 0x90, 0x21, 0xFA, 0xD1, 0x0C, 0x64, 0x19, 0x2B, 0x86, 0x58, 0x9B, 0x17, 0x2B, 0x10, 0x05, 0xB8, 0xD1, 0xF8, 0x4C, 0xEF, 0x53, 0x4C, 0xD5, 0x4E, 0x5C, 0xAE, 0x86, 0xEF, 0x92, 0x7B, 0x90, 0xD1, 0xE0, 0x62, 0xFD, 0x7C, 0x54, 0x55, 0x9E, 0xE0, 0xE7, 0xBE, 0xFA, 0x3F, 0x9E, 0x15, 0x6F, 0x6C, 0x38, 0x4E, 0xAF, 0x07, 0x0C, 0x61, 0xAB, 0x51, 0x5E, 0x23, 0x53, 0x14, 0x18, 0x88, 0xCB, 0x6F, 0xCB, 0xC5, 0xD6, 0x30, 0xF4, 0x06, 0xED, 0x24, 0x23, 0xEF, 0x25, 0x6D, 0x00, 0x91, 0x77, 0x24, 0x9B, 0xE5, 0xA3, 0xC0, 0x27, 0x90, 0xC2, 0x97, 0xF7, 0x74, 0x9D, 0x6F, 0x17, 0x83, 0x7E, 0xB5, 0x37, 0xDE, 0x51, 0xE8, 0xD7, 0x1C, 0xE1, 0x56, 0xD9, 0x56, 0xC8, 0xC3, 0xC3, 0x20, 0x9D, 0x64, 0xC3, 0x2F, 0x8C, 0x91, 0x92, 0x30, 0x6F, 0xDB };
const char ExponentCON[0x4] = { 0x00, 0x01, 0x00, 0x01 };
const char PCON[0x40] = { 0xCC, 0xE7, 0x5D, 0xFE, 0x72, 0xB6, 0xFD, 0xE7, 0x1D, 0xE3, 0x1A, 0x0E, 0xAC, 0x33, 0x7A, 0xB9, 0x21, 0xE8, 0x8A, 0x84, 0x9B, 0xDA, 0x9F, 0x1E, 0x58, 0x34, 0x68, 0x7A, 0xB1, 0x1D, 0x7E, 0x1C, 0x18, 0x52, 0x65, 0x7B, 0x97, 0x8E, 0xA7, 0x6A, 0x9D, 0xEE, 0x5A, 0x77, 0x52, 0x3B, 0x71, 0x8F, 0x33, 0xD0, 0x49, 0x5E, 0xC3, 0x30, 0x39, 0x72, 0x36, 0xBF, 0x1D, 0xD9, 0xF2, 0x24, 0xE8, 0x71 };
const char QCON[0x40] = { 0xCB, 0xCA, 0x58, 0x74, 0xD4, 0x03, 0x62, 0x93, 0x06, 0x50, 0x1F, 0x42, 0xF6, 0xAA, 0x59, 0x36, 0xA7, 0xA1, 0xF3, 0x97, 0x5C, 0x9A, 0xC8, 0x6A, 0x27, 0xCF, 0x85, 0x05, 0x2A, 0x66, 0x41, 0x6A, 0x7F, 0x2F, 0x84, 0xC8, 0x18, 0x13, 0xC6, 0x1D, 0x8D, 0xC7, 0x32, 0x2F, 0x72, 0x19, 0x3F, 0xA4, 0xED, 0x71, 0xE7, 0x61, 0xC0, 0xCF, 0x61, 0xAE, 0x8B, 0xA0, 0x68, 0xA7, 0x7D, 0x83, 0x23, 0x0B };
const char DPCON[0x40] = { 0x4C, 0xCA, 0x74, 0xE6, 0x74, 0x35, 0x72, 0x48, 0x58, 0x62, 0x11, 0x14, 0xE8, 0xA2, 0x4E, 0x5E, 0xED, 0x7F, 0x49, 0xD2, 0x52, 0xDA, 0x87, 0x01, 0x87, 0x4A, 0xF4, 0xD0, 0xEE, 0x69, 0xC0, 0x26, 0x65, 0x53, 0x13, 0xE7, 0x52, 0xB0, 0x4A, 0xBB, 0xE1, 0x3E, 0x3F, 0xB7, 0x32, 0x21, 0x46, 0xF8, 0xC5, 0x11, 0x4D, 0x3D, 0xEF, 0x66, 0xB6, 0x50, 0xC0, 0x85, 0xB5, 0x79, 0x45, 0x8F, 0x61, 0x71 };
const char InverseQCON[0x40] = { 0x28, 0x6A, 0xBB, 0xD1, 0x93, 0x95, 0x94, 0x1A, 0x6E, 0xED, 0xD7, 0x0E, 0xC0, 0x61, 0x2B, 0xC2, 0xEF, 0xE1, 0x86, 0x3D, 0x34, 0x12, 0x88, 0x6F, 0x94, 0xA4, 0x48, 0x6E, 0xC9, 0x87, 0x1E, 0x46, 0x00, 0x46, 0x00, 0x52, 0x8E, 0x9F, 0x47, 0xC0, 0x8C, 0xAB, 0xBC, 0x49, 0xAC, 0x5B, 0x13, 0xF2, 0xEC, 0x27, 0x8D, 0x1B, 0x6E, 0x51, 0x06, 0xA6, 0xF1, 0x62, 0x1A, 0xEB, 0x78, 0x2E, 0x88, 0x48 };
const char DCON[0x80] = { 0x9B, 0xF9, 0xDE, 0xC2, 0x45, 0x93, 0x4C, 0x4C, 0xAC, 0x48, 0x2B, 0xA8, 0x4D, 0xFC, 0xD7, 0xED, 0xB2, 0xFB, 0x72, 0xE9, 0xEA, 0xC1, 0x88, 0x39, 0x07, 0x2A, 0x6F, 0x34, 0x07, 0x81, 0x97, 0x7E, 0xCD, 0xFA, 0x21, 0x02, 0xF5, 0xDD, 0x30, 0xDD, 0x22, 0x4A, 0xB3, 0x41, 0xE5, 0x89, 0x80, 0x73, 0xC4, 0xAF, 0x90, 0x9E, 0x2B, 0x50, 0x8A, 0x0A, 0xD4, 0x6E, 0xBD, 0x0F, 0x15, 0x79, 0x37, 0x95, 0xE8, 0x3D, 0xCF, 0x4C, 0x6D, 0xFF, 0x51, 0x65, 0xE7, 0x90, 0xC1, 0xAC, 0x2D, 0xC6, 0xEB, 0x47, 0x19, 0x2D, 0xD0, 0x58, 0x74, 0x79, 0xAC, 0x08, 0x1C, 0xA3, 0x1D, 0xD0, 0xCE, 0x39, 0x2E, 0xC3, 0xFA, 0x66, 0xEF, 0xC7, 0x8E, 0x10, 0x2F, 0xE4, 0xA1, 0xE7, 0x4E, 0xA8, 0x42, 0xF0, 0xF4, 0xFD, 0x10, 0xA6, 0x67, 0x64, 0xCB, 0x3A, 0x6D, 0x4D, 0x51, 0xEC, 0x1F, 0x9D, 0x56, 0x26, 0xC2, 0xFC };
const char DQCON[0x40] = { 0xAF, 0xDC, 0x46, 0xE7, 0x52, 0x8A, 0x35, 0x47, 0xA1, 0x1C, 0x05, 0x4E, 0x39, 0x24, 0x99, 0xE6, 0x43, 0x54, 0xCB, 0xAB, 0xE3, 0xDB, 0x22, 0x76, 0x11, 0x32, 0xD0, 0x9C, 0xBB, 0x91, 0x10, 0x84, 0x81, 0x8B, 0x15, 0x2F, 0xC3, 0x2F, 0x55, 0x38, 0xED, 0xBF, 0x67, 0x3C, 0x70, 0x5E, 0xFF, 0x80, 0x28, 0xF3, 0xB1, 0x73, 0xB6, 0xFA, 0x7F, 0x56, 0x2B, 0xE1, 0xDA, 0x4E, 0x27, 0x4E, 0xC2, 0x2F };
// set the params
CryptoPP::AutoSeededRandomPool rng;
InvertibleRSAFunction params;
Integer integ(ModulusCON);
params.SetModulus(integ);
Integer integ1(ExponentCON);
params.SetPublicExponent(integ1);
Integer integ2(PCON);
params.SetPrime1(integ2);
Integer integ3(QCON);
params.SetPrime2(integ3);
Integer integ4(DPCON);
params.SetModPrime1PrivateExponent(integ4);
Integer integ5(InverseQCON);
params.SetMultiplicativeInverseOfPrime2ModPrime1(integ5);
Integer integ6(DCON);
params.SetPrivateExponent(integ6);
Integer integ7(DQCON);
params.SetModPrime2PrivateExponent(integ7);
// create the keys
RSA::PrivateKey privateKey(params);
RSA::PublicKey publicKey(params);
CryptoPP::RSASSA_PKCS1v15_SHA_Signer signer(privateKey);
unsigned char data[20] = { 0x6F, 0x9F, 0x07, 0x04, 0xE2, 0x1A, 0xF7, 0xB8, 0xB2, 0x4F, 0x8D, 0x66, 0x49, 0xA1, 0x09, 0xA7, 0xB2, 0x22, 0x3C, 0xF9 };
BYTE *signature = new BYTE[0x80];
signer.SignMessage(rng, data, 20, signature);
Based on what I know, Crypto++'s 'RSASSA_PKCS1v15_SHA_Signer' is what I want equivalent to C#'s 'RSAPKCS1SignatureFormatter' and setting the hash algorithm to SHA1.
The error it throws is:
Unhandled exception at at 0x7646B9BC in proj.exe: Microsoft C++ exception: > CryptoPP::PK_SignatureScheme::KeyTooShort at memory location 0x0040EF18.
Thanks for any help, Hetelek.
I can't answer as to why this works in C#, but as for Crypto++, there are a couple of issues.
Firstly, you're probably invoking the wrong constructor of Integer. I guess you want this one which converts from big-endian byte array:
Integer (const byte *encodedInteger, size_t byteCount, Signedness s=UNSIGNED)
but are using this one which convert from a string in base 2, 8, 10, or 16 (in your case base 10).
So, using ExponentCON as an example, you should do:
const int ExponentSize(0x4);
const byte ExponentCON[ExponentSize] = { 0x00, 0x01, 0x00, 0x01 };
Integer integ1(ExponentCON, ExponentSize);
or possibly better still:
std::string ExponentCON("101h"); // <-- Note trailing 'h' indicating hex encoding
Integer integ1(ExponentCON.c_str());
Next, the members of InvertibleRSAFunction must satisfy certain conditions in order to qualify as a valid key. These can be seen by stepping through the InvertibleRSAFunction::Validate function and I assume check for the conditions described here.
params.Validate(rng, 3); // Returns false for your input data
There are some helper functions which are designed to avoid having to set everything explicitly as you're doing. I don't know if these are suitable for you, but I'm referring to InvertibleRSAFunction::GenerateRandomWithKeySize and the overloaded InvertibleRSAFunction::Initialize.
The Crypto++ Wiki describes the use of these functions with example code.
TLDR: your private exponent, d, is wrong in your sample program. You have other, more obvious problems, too. But d is causing the mathematical problems.
And it begs the question, how did that work in C#? The math does not change across computer languages and runtimes.
The first problem is the declarations using chars:
...
const char ExponentCON[0x4] = { 0x00, 0x01, 0x00, 0x01 };
...
This causes you to use the constructors for ASCII strings, which is the wrong Integer constructor. It results in at least two issues:
// Added for testing
if (integ != integ2 * integ3)
{
cerr << "error: n != p*q" << endl;
}
// Added for testing
params.ThrowIfInvalid(prng, 3);
When running the program, ThrowIfInvalid validates the parameters and its the source of CryptoMaterial: ...:
error: n != p*q
CryptoMaterial: this object contains invalid values
The const char need to be changed to const byte. Then:
Integer integ(ModulusCON, sizeof(ModulusCON));
params.SetModulus(integ);
Integer integ1(ExponentCON, sizeof(ExponentCON));
params.SetPublicExponent(integ1);
Integer integ2(PCON, sizeof(PCON));
params.SetPrime1(integ2);
Integer integ3(QCON, sizeof(QCON));
params.SetPrime2(integ3);
...
With that change in place, this error message from above disappears: error: n != p*q. But the CryptoMaterial: this object contains invalid values remains.
The second problem appears to be some of your private key parameters are not correct. You can see what tests InvertibleRSAFunction::Validate is performing by looking at the source code in rsa.cpp near line 250.
You can partially side step it by using Initialize that takes {n,e,d}, and let Initialize factor and solve:
Integer n(ModulusCON, sizeof(ModulusCON));
Integer e(ExponentCON, sizeof(ExponentCON));
Integer d(DCON, sizeof(DCON));
params.Initialize(n,e,d);
params.ThrowIfInvalid(prng, 3);
However, that results in:
InvertibleRSAFunction: input is not a valid RSA private key
Next, check p and q. #include <nbtheory.h>, and then:
Integer p(PCON, sizeof(PCON));
Integer q(QCON, sizeof(QCON));
cout << "P is prime: " << (VerifyPrime(prng, p, 10) ? "yes" : "no") << endl;
cout << "Q is prime: " << (VerifyPrime(prng, q, 10) ? "yes" : "no") << endl;
It results in:
$ ./test.exe
P is prime: yes
Q is prime: yes
At this point, it appears the problem is with one of the exponents.
Next, assume e is relatively prime to phi, #include <modarith.h>, and then:
Integer n(ModulusCON, sizeof(ModulusCON));
Integer p(PCON, sizeof(PCON));
Integer q(QCON, sizeof(QCON));
Integer e(ExponentCON, sizeof(ExponentCON));
Integer phi = (p-1)*(q-1);
ModularArithmetic ma(phi);
Integer d = ma.MultiplicativeInverse(e);
params.Initialize(n,e,d);
params.ThrowIfInvalid(prng, 3);
cout << "Validated parameters" << endl;
It results in:
$ ./test.exe
Validated parameters
So, the problem is with your d exponent. It is easy enough to print with cout << std::hex << d << endl:
$ ./test.exe
Validated parameters
174bcc91cc08400b470a9357e7fd23db2384e4219af4dedc56a0afdc3e796abd965f16c680954549
b4526f01a2c9d7b727620f3ba6c848f19bd9210650ae62593249d7a4e0522ad48aea559d4f6a1f3f
6ae9953bed7c947e273d455a4982523dd90640b0a25572ae8c5e064e39807ddf778af96afd492999
acc40919a4d4f601h
As you can see, the first octet of the calculated d is 0x17, but the first octet of the d you provided is 0x9B.
Also, you might want to do something like the following:
unsigned char data[20] = { 0x6F, 0x9F, 0x07, 0x04, 0xE2, 0x1A, 0xF7, 0xB8, 0xB2, 0x4F,
0x8D, 0x66, 0x49, 0xA1, 0x09, 0xA7, 0xB2, 0x22, 0x3C, 0xF9 };
const size_t req = signer.MaxSignatureLength(sizeof(data));
byte signature[req];
const size_t used = signer.SignMessage(prng, data, 20, signature);
// Trim 'signature' to 'used'