Re: how to use message authentication code with Crypto++ as described in FAQ?

[Jeffrey Walton]

Hi Adam,

A MAC is a keyed digest. It does not offer confidentiality - only
authentication.

Jeff

#include "sha.h"
using CryptoPP::SHA1;
#include "hmac.h"
using CryptoPP::HMAC;

#include <string>
using std::string;

int main(int argc, char* argv[])
{
    byte key [ HMAC<SHA1>::DIGESTSIZE ];
    byte digest [ HMAC<SHA1>::DIGESTSIZE ];
    memset( key, 0, sizeof(key) );

    HMAC<SHA1> hmac( key, sizeof(key ) );
    string plain = "Hello World", mac;

    hmac.Update( (byte*)plain.c_str(), plain.size() );
    hmac.Final( digest );

    // Wrap in a string for convenience
    mac = string( (char*)digest, sizeof(digest ) );

    /* ======================================== *\
    \* ======================================== */

    HMAC<SHA1> verifier( key, sizeof(key) );
    bool b = false;

    // b: true
    b = verifier.VerifyDigest( digest,
        (byte*)plain.c_str(), plain.size() );

    // b: true
    verifier.Restart();
    b = verifier.VerifyDigest( (byte*)mac.c_str(),
        (byte*)plain.c_str(), plain.size() );

    // b: false
    verifier.Restart();
    plain = "hello world";
    b = verifier.VerifyDigest( (byte*)mac.c_str(),
        (byte*)plain.c_str(), plain.size() );

    return 0;
}


On Mon, Jun 9, 2008 at 5:57 PM, Adam Harding <[EMAIL PROTECTED]> wrote:
>
> Thanks for reply.
>
> I have been looking at the HMAC-SHA test function in .cpp. But how do
> I go about actually using this piece of code to compute and then print
> a digest? Cant seem to figure it out.
>
> Many thanks.
>
> [SNIP]

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