I wanted to put that on the wiki, but registration doesn't quite work
for me there...
Here is code to generate private/public key pair and then sign and
verify a message.
using namespace CryptoPP;
AutoSeededRandomPool rng;
// Generating private key
ECIES<ECP>::PrivateKey privateKey;
privateKey.Initialize(rng, ASN1::secp160r1());
// Generating matching public key
ECIES<ECP>::PublicKey publicKey;
privateKey.MakePublicKey(publicKey);
// Signing a message
ECDSA<ECP>::Signer signer(privateKey);
std::string message="message";
std::string signature;
StringSource(message, true, new SignerFilter(rng, signer, new
StringSink(signature)));
// signature contains bytes, not ascii string. Just use base32 or hex
encoder if needed.
// Verifying message
ECDSA<ECP>::Verifier verifier(publicKey);
bool isValid = verifier.VerifyMessage((const byte*)message.data(),
message.size(), (const byte*)signature.data(), signature.size());
Of course for this to be usefull you'll need to load and save keys:
Saving:
ECIES<ECP>::PrivateKey privateKey;
// generate key ...
std::string tmp;
StringSink sink(tmp);
privateKey.Save(sink);
std::string base32encodedKey;
StringSource(tmp, true, new Base32Encoder(new StringSink
(base32encodedKey)));
Loading:
ECIES<ECP>::PrivateKey privateKey;
ByteQueue bq;
StringSource(base32encodedKey, true, new Base32Decoder(new Redirector
(bq)));
privateKey.Load(bq);
Same with public keys.
On Jul 18, 2:57 am, bobby <[email protected]> wrote:
> Hello,
>
> I am interested in using ECC or more probably ECDSA to verify a string
> transmitted by a server. The way I'd like it to work is that the
> server will create any arbitrary text string. It'll take the string
> and hash it and then calculate a signature using some private key.
> Then it will transmit the string and the signature and I'd like the
> client to be able to verify that the string and signature match using
> only the public key information. My only other requirement is that I
> need to be able to generate new private/public key pairs from time to
> time. I also need fairly short key sizes (less than 160 bits).
>
> From my limited knowledge, it sounds like ECDSA is what I want.
> Unfortunately, I am not very math savvy and I start to get lost once
> people start bringing up the formulas. I am also having a somewhat
> difficult time understanding how all the Crypto++ code works with
> regards to ECDSA.
>
> So does anyone have any example code that shows this kind of
> functionality?
>
> Thanks!
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