Thank you Jeff. I appreciate it a lot.
Basically I would like to convert the code in the first example (below) to
use anything safe to first sign the message with a private key and then
verify and extract with public key (the 'recovered' variable below).
No need for any large content, yeah.
Olli
int main(int argc, char* argv[])
{
try {
////////////////////////////////////////////////
// Generate keys
AutoSeededRandomPool rng;
InvertibleRSAFunction parameters;
parameters.GenerateRandomWithKeySize( rng, 1024 );
RSA::PrivateKey privateKey( parameters );
RSA::PublicKey publicKey( parameters );
// Signing
RSASS<PSSR, SHA1>::Signer signer( privateKey );
RSASS<PSSR, SHA1>::Verifier verifier( publicKey );
// Setup
byte message[] = "RSA-PSSR Test";
size_t messageLen = sizeof(message);
////////////////////////////////////////////////
// Sign and Encode
SecByteBlock signature(signer.MaxSignatureLength(messageLen));
size_t signatureLen = signer.SignMessageWithRecovery(rng, message,
messageLen, NULL, 0, signature);
////////////////////////////////////////////////
// Verify and Recover
SecByteBlock recovered(
verifier.MaxRecoverableLengthFromSignatureLength(signatureLen)
);
DecodingResult result = verifier.RecoverMessage(recovered, NULL,
0, signature, signatureLen);
if (!result.isValidCoding) {
throw Exception( Exception::OTHER_ERROR, "Invalid Signature" );
}
////////////////////////////////////////////////
// Use recovered message
size_t recoveredLen = result.messageLength;
assert( 0 == memcmp( message, (const byte*)recovered,
std::min( messageLen, recoveredLen ) ) );
} // try
catch( CryptoPP::Exception&e ) {
std::cerr << "Error: " << e.what() << endl;
}
return 0;
}
On Saturday, January 12, 2019 at 1:16:27 PM UTC+2, Olli Savolainen wrote:
>
> Hi there,
>
> I'm using crypto++ according to the RSA-PSSR-Filter-Test.zip example from
> this link and it works:
> http://marko-editor.com/articles/cryptopp_sign_string/
>
> I'm trying to find something I can use reliably for signing a message with
> private key and verifying its origin with public key programmatically in a
> Qt app.
>
> I am happy I can actually get the message extracted while verifying the
> signature:
>
> StringSource(signature, true,
> new SignatureVerificationFilter(
> verifier,
> new StringSink(recovered),
> SignatureVerificationFilter::THROW_EXCEPTION |
> SignatureVerificationFilter::PUT_MESSAGE) // SignatureVerificationFilter
> ); // StringSource
>
> assert(ui->plainTextEdit->toPlainText().toStdString() == recovered);
>
> But SHA1 is unsafe.
>
> Then I found this example with Whirlpool. However, it doesn't seem to
> extract the actual original message, just claims to verify it.Does this
> code actually verify the message though? The ArraySink usage seems a bit
> esoteric to me so I can't tell.
> http://marko-editor.com/articles/cryptopp_sign_string/
>
> bool result = false;
> Verifier verifier(publicKey);
> CryptoPP::StringSource ss2(decodedSignature + aMessage, true,
> new
> CryptoPP::SignatureVerificationFilter(verifier,
> new CryptoPP::ArraySink((byte*)&result,
> sizeof(result))));
>
> return result;
>
> I tried to convert the code to be similar to the SHA1 example but this
> does not extract any message:
>
> CryptoPP::StringSource ss2(decodedSignature, true,
> new CryptoPP::SignatureVerificationFilter(verifier,
> new StringSink(recovered)));
>
> Is it possible to convert this code with Whirlpool to actually extract the
> message from the signature, or is the actual message not contained in the
> signature although it appears to be PSSR?
>
> I am also wondering about the usage of 'new' allocations here; does this
> code actually leak memory?
>
> My apologies for any erroneous terminology; I am not in the security field.
> I hope linking to the full examples instead of attaching to them to this
> message is enough, it seemed extraneous to attach files here that are
> already publicly available. I already asked this on stackoverflow before,
> feel free to respond there if you like.
>
> https://stackoverflow.com/questions/54033029/using-crypto-to-sign-using-private-key-sha1-vs-whirlpool
>
> Kind regards,
> Olli Savolainen
>
>
>
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