SM3

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SM3
Documentation
#include <cryptopp/sm3.h>

SM3 is cryptographic hash function designed by Xiaoyun Wang, et al. The hash is part of the Chinese State Cryptography Administration portfolio. Also see Internet Draft, SM3 Hash Function and Reference implementation using OpenSSL.

All Crypto++ hashes derive from HashTransformation. The base class provides functions like Update, Final and Verify. You can swap-in any hash for any other hash in your program.

Sample Programs

There are five sample programs. The first prints information about the hash. The second creates a hash using SM3 class. The third creates a hash using a pipeline. The fourth and fifth examples show how to verify an existing digest.

The examples below use SM3, but you can swap-in any hash function, like PanamaHash, SM3 or BLAKE2s.

The first example dumps the name, digest size and internal block size of the hash.

#include "cryptlib.h"
#include "sm3.h"
#include <iostream>

int main (int argc, char* argv[])
{
    using namespace CryptoPP;

    SM3 hash;
	
    std::cout << "Name: " << hash.AlgorithmName() << std::endl;
    std::cout << "Digest size: " << hash.DigestSize() << std::endl;
    std::cout << "Block size: " << hash.BlockSize() << std::endl;

    return 0; 
}

Running the program results in the following. In general you should use DigestSize and avoid BlockSize. BlockSize is usually not required by a program. In the case of SHAKE the block size is the rate r.

$ ./test.exe
Name: SM3
Digest size: 32
Block size: 64

The second example creates a hash using the hash object and member functions. You add data using Update and you calculate the hash using Final. Calling Final resets the hash so you don't need to do it manually.

using namespace CryptoPP;
HexEncoder encoder(new FileSink(std::cout));

std::string msg = "Yoda said, Do or do not. There is not try.";
std::string digest;

SM3 hash;
hash.Update((const byte*)msg.data(), msg.size());
digest.resize(hash.DigestSize());
hash.Final((byte*)&digest[0]);

std::cout << "Message: " << msg << std::endl;

std::cout << "Digest: ";
StringSource(digest, true, new Redirector(encoder));
std::cout << std::endl;

Running the program results in the following.

$ ./test.exe
Message: Yoda said, Do or do not. There is not try.
Digest: 6BB5FF84416DC1EDF21C7B0C36D7ADFDEBE9378702A8982DD6FF0842188B67A5

You can also obtain a truncated hash rather than the full hash using TruncatedFinal.

std::cout << "Message: " << msg << std::endl;

hash.Update((const byte*)msg.data(), msg.size());
digest.resize(hash.DigestSize()/2);
hash.TruncatedFinal((byte*)&digest[0], digest.size());

std::cout << "Digest: ";
StringSource(digest, true, new Redirector(encoder));
std::cout << std::endl;

The program produces the following result.

$ ./test.exe
Message: Yoda said, Do or do not. There is not try.
Digest: 6BB5FF84416DC1EDF21C7B0C36D7ADFD

Using a pipeline produces the same result. It relieves you of calling Update and Final manually. The code also uses a HashFilter, which has its own wiki page at HashFilter.

std::string msg = "Yoda said, Do or do not. There is not try.";
std::string digest;

StringSource(msg, true, new HashFilter(hash, new StringSink(digest)));

std::cout << "Message: " << msg << std::endl;

std::cout << "Digest: ";
StringSource(digest, true, new Redirector(encoder));
std::cout << std::endl;

Running the program results in the following.

$ ./test.exe
Message: Yoda said, Do or do not. There is not try.
Digest: 6BB5FF84416DC1EDF21C7B0C36D7ADFDEBE9378702A8982DD6FF0842188B67A5

The fourth program verifies an existing hash using the hash object. Notice the program proceeds as if the hash is going to be calculated. But rather than calling Final to retrieve the hash, Verify is called to verify the existing hash.

SM3 hash;
hash.Update((const byte*)msg.data(), msg.size());
bool verified = hash.Verify((const byte*)digest.data());

if (verified == true)
    std::cout << "Verified hash over message" << std::endl;
else
    std::cout << "Failed to verify hash over message" << std::endl;

The final program verifies an existing hash using a pipeline. The code uses a HashVerificationFilter, which has its own wiki page at HashVerificationFilter.

bool result;
StringSource(digest+msg, true, new HashVerificationFilter(hash,
                 new ArraySink((byte*)&result, sizeof(result))));

if (result == true)
    std::cout << "Verified hash over message" << std::endl;
else
    std::cout << "Failed to verify hash over message" << std::endl;

Running the program results in the following output.

$ ./test.exe
Message: Yoda said, Do or do not. There is not try.
Digest: 6BB5FF84416DC1EDF21C7B0C36D7ADFDEBE9378702A8982DD6FF0842188B67A5
Verified hash over message

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