bool EMSA1::verify(const secure_vector<uint8_t>& input,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
try {
if(raw.size() != m_hash->output_length())
throw Encoding_Error("EMSA1::encoding_of: Invalid size for input");
// Call emsa1_encoding to handle any required bit shifting
const secure_vector<uint8_t> our_coding = emsa1_encoding(raw, key_bits);
if(our_coding.size() < input.size())
return false;
const size_t offset = our_coding.size() - input.size(); // must be >= 0 per check above
// If our encoding is longer, all the bytes in it must be zero
for(size_t i = 0; i != offset; ++i)
if(our_coding[i] != 0)
return false;
return same_mem(input.data(), &our_coding[offset], input.size());
}
catch(Invalid_Argument)
{
return false;
}
}
bool EMSA1::verify(const secure_vector<byte>& coded,
const secure_vector<byte>& raw, size_t key_bits)
{
try {
if(raw.size() != m_hash->output_length())
throw Encoding_Error("EMSA1::encoding_of: Invalid size for input");
secure_vector<byte> our_coding = emsa1_encoding(raw, key_bits);
if(our_coding == coded) return true;
if(our_coding.empty() || our_coding[0] != 0) return false;
if(our_coding.size() <= coded.size()) return false;
size_t offset = 0;
while(offset < our_coding.size() && our_coding[offset] == 0)
++offset;
if(our_coding.size() - offset != coded.size())
return false;
for(size_t j = 0; j != coded.size(); ++j)
if(coded[j] != our_coding[j+offset])
return false;
return true;
}
catch(Invalid_Argument)
{
return false;
}
}
secure_vector<uint8_t> EMSA1::encoding_of(const secure_vector<uint8_t>& msg,
size_t output_bits,
RandomNumberGenerator&)
{
if(msg.size() != hash_output_length())
throw Encoding_Error("EMSA1::encoding_of: Invalid size for input");
return emsa1_encoding(msg, output_bits);
}