Using the aes128 class

The aes128 class provides a simple AES-128 encryption/decryption implementation.

The aes128 class inherits from the encryption class. The setKey()/setIv() methods set the encryption key and initialization vector, or setRandomKey()/setRandomIv() can be used to generate random values. The append() method feeds in data, getEncryptedData() encrypts and returns the result, and getDecryptedData() decrypts and returns the result. The clear() method resets the data while preserving the key and initialization vector, and reset() clears everything. The isSupported() method can be used to determine if AES-128 is available on the current platform.

The key size and initialization vector size are both 16 bytes for AES-128. These sizes can be retrieved using getKeySize() and getIvSize().

The default block cipher mode is CBC, but this can be changed using setBlockCipherMode().

The following example encrypts a string, prints the encrypted data in hexadecimal, decrypts it back, clears and encrypts a different string.

#include <rudiments/aes128.h>
#include <rudiments/charstring.h>
#include <rudiments/stdio.h>

int main(int argc, const char **argv) {

	aes128	a;

	// check whether aes128 is supported
	if (!a.isSupported()) {
		stdoutput.write("aes128 is not supported\n");
		return 1;
	}


	// set a random key and initialization vector
	a.setRandomKey();
	a.setRandomIv();


	// encrypt some data
	const char	*data="hello world";
	a.append((const byte_t *)data,charstring::getLength(data));

	const byte_t	*enc=a.getEncryptedData();
	uint64_t	encsize=a.getEncryptedDataSize();

	// print the encrypted data in hexadecimal
	stdoutput.printf("encrypted: ");
	for (uint64_t i=0; i<encsize; i++) {
		stdoutput.printf("%02x",enc[i]);
	}
	stdoutput.write('\n');


	// decrypt using the same key and initialization vector
	aes128	b;
	b.setKey(a.getKey(),a.getKeySize());
	b.setIv(a.getIv(),a.getIvSize());

	b.append(enc,encsize);

	const byte_t	*dec=b.getDecryptedData();
	uint64_t	decsize=b.getDecryptedDataSize();

	stdoutput.printf("decrypted: %.*s\n",decsize,dec);


	// clear and encrypt different data
	a.clear();

	data="goodbye world";
	a.append((const byte_t *)data,charstring::getLength(data));

	enc=a.getEncryptedData();
	encsize=a.getEncryptedDataSize();

	stdoutput.printf("encrypted: ");
	for (uint64_t i=0; i<encsize; i++) {
		stdoutput.printf("%02x",enc[i]);
	}
	stdoutput.write('\n');

	// decrypt
	b.clear();
	b.append(enc,encsize);

	dec=b.getDecryptedData();
	decsize=b.getDecryptedDataSize();

	stdoutput.printf("decrypted: %.*s\n",decsize,dec);
}