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rsa-cpp-encrypt is a simple textbook RSA library for C++. The library is capable of generating 2048 bit RSA key pairs, encrypting, decrypting and also exporting/importing keys in PKCS#1 format. The implementation usesbiging-x86cpp and is only compatible with x86 architecture CPUs

Add the foldersbigint andrsa-crypt from/include in your include path. If you want to compile the library from source, includeASN1.cpp andRSACipher.cpp from the/src folder. Alternatively, you can compile the source code to a static library and include it that way.

To create a cipher, you can provide a public or a private key. If you want to generate a new key, you can use thegenPrivKey() function. The function generates a random key you can seed with the Csrand() function.

srand(1234);RSACipherrsa(genPrivKey());

Alternatively, you can create an empty RSA cipher, then import a public or a private key. The import and export functions only take PKCS#1 format RSA keys.

RSACipher rsa;rsa.importPubKey("-----BEGIN RSA PUBLIC KEY-----\n""MIIBCgKCAQEAq ...... 7dcERQIDAQAB""\n-----END RSA PUBLIC KEY-----");

RSACipher rsa;rsa.importPrvKey("-----BEGIN RSA PRIVATE KEY-----\n""MIIEpQIBAAKCA ...... dMbKLovrxqU=""\n-----END RSA PRIVATE KEY-----");

You can export a private or a public key into a character array buffer. You also need to provide the size of the buffer. The key is exported in PKCS#1 format

char buff[2048];rsa.exportPubKey(buff,2048);// Prints PKCS#1 formatted Public Keycout << buff << endl;

Once you have created an RSA cipher, you can encrypt or decrypt 256 bytes of data. For this, the cipher expects a 256 byte large Big Integer. The result of encryption and decryption is also a Big Integer.

BigInt<256>message("123456");BigInt<256> ciphertext = rsa.encrypt(message);BigInt<256> plaintext  = rsa.decrypt(ciphertext);cout<< message <<"\n\n";cout<< ciphertext.toString(64) <<"\n\n";cout<< plaintext <<"\n\n";

Output:123456S12DtydRI2r72ouUWsHSVat5lfuU45bYVl+W3aPgcKnnlX05w2qmlgjN+MMsURnmA0/SAM+ZPvBej8Vvs3i0XwT5J6Q+qR6k7SQZ6qdPM8tiqaHeJ+9tVMLu+NJ4NTmtUypFxIufm0agvx3RyK4EmhOOw7dZC9CqadnAWxDYDpG6eVkH+PO2qUzxVddy4Iojj/29kjo2p3TzvSoE7lMoAT3trW3Er+vhjRpK/saFD8EnsTc//bfQ87EFUxt81p+e9uGiXz4Cd6aWUTXNypo3uy+VaLg9+9yQ1WVdxPrv/OMFNsE7XsFW9DgfZHGZy+4T0IekUvEjGf2+2b8ciYXpZA==123456