CODEWITHSUNDEEP
c++crypto++
Martin Dusek
Martin Dusek

Reputation: 1292

Crypto++ verify large file signature

I use this code to verify a message with crypto++:

CryptoPP::ECDSA<CryptoPP::ECP, CryptoPP::SHA256>::Verifier verifier(key);
bool result = verifier.VerifyMessage( (const CryptoPP::byte*)message.data(), message.length(), (const CryptoPP::byte*)signature.data(), signature.length() );

Now I would like to verify a signature I previously created for a file. The file is quite big (GB) and I don't want to load it to memory in one piece (to message variable).

Is there a way crypto++ can verify large file's signature?

Upvotes: 1

Views: 674

Answers (1)

Martin Dusek
Martin Dusek

Reputation: 1292

This code does what I need:

 CryptoPP::ECDSA<CryptoPP::ECP, CryptoPP::SHA256>::PublicKey key; key.Load(queue);
 CryptoPP::ECDSA<CryptoPP::ECP, CryptoPP::SHA256>::Verifier verifier(key);

 CryptoPP::SignatureVerificationFilter verificationFilter(verifier, NULL, CryptoPP::SignatureVerificationFilter::SIGNATURE_AT_BEGIN);
 CryptoPP::FileSource fileSource( file, false, new CryptoPP::Redirector(verificationFilter));
 CryptoPP::StringSource signatureSource( (const CryptoPP::byte*)signature.data(), signature.length(), false, new CryptoPP::Redirector(verificationFilter));
 signatureSource.Pump(signature.length());
 fileSource.PumpAll();

 return verificationFilter.GetLastResult();

Upvotes: 1

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