AES-GCM算法

AES-GCM算法简介

AES-GCM算法是带认证和加密的算法，同时可以对给定的原文，生成加密数据和认证码。参数如下：

1）带加密的原文、2）存储加密后密文、3）IV向量、4）生成的消息验证码tag、5）额外的消息认证数据aad，通信双方需要共享；

整个AES-GCM算法代码如下：

#include <stdio.h>
#include <string.h>
#include <errno.h>

#include <ica_api.h>

#define AES_CIPHER_BLOCK_SIZE  16

/* 本测试demo用了一个静态的key
 *
 * Note: AES-128 key size is 16 bytes (AES_KEY_LEN128)
 */
unsigned char aes_key[] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
};

/* 带加密的数据原文.
 */
unsigned char plain_data[] = {
	0x55, 0x73, 0x69, 0x6e, 0x67, 0x20, 0x6c, 0x69,
	0x62, 0x69, 0x63, 0x61, 0x20, 0x69, 0x73, 0x20,
	0x73, 0x6d, 0x61, 0x72, 0x74, 0x20, 0x61, 0x6e,
	0x64, 0x20, 0x65, 0x61, 0x73, 0x79, 0x21, 0x00
};

/* 初始化的IV向量. The initialization vector
 * size must be greater than 0 and less than 2**61. A length of
 * 12 is recommended.
 */
unsigned char iv[12] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0A, 0x0B
};

/* aad是额外的认证数据,aad数组用于计算生成AES-GCM消息的认证码，不用于加密。
 */
unsigned char aad[] = {
	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
	0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F
};

/* Prints hex values to standard out. */
static void dump_data(unsigned char *data, unsigned long length);
/* Prints a description of the return value to standard out. */
static int handle_ica_error(int rc);

int main(char **argv, int argc)
{
	int rc;

	/* tag数组存储者明文数据和aad变量的消息验证码.
	 * Note: The authentication strength depends on the length of the
	 *       authentication tag
	 */
	unsigned char tag[16];

	unsigned char cipher_data[sizeof(plain_data)];     //存储者AES-GCM加密后的数据
	unsigned char decrypt_data[sizeof(plain_data)];    //存储者AES-GCM解密后的数据

	/* Dump key, iv, aad and plain data to standard output, just for
	 * a visual control.
	 */
	printf("AES key:\n");
	dump_data(aes_key, sizeof(aes_key));
	printf("IV:\n");
	dump_data(iv, sizeof(iv));
	printf("AAD:\n");
	dump_data(aad, sizeof(aad));
	printf("plain data:\n");
	dump_data(plain_data, sizeof(plain_data));	

	/* 使用AES-GCM将明文数据plain_data加密成密文cipher_data，同时根据plain_data和aad变量生成消息验证码tag变量*/
    //ICA_ENCRYPT=0
	rc = ica_aes_gcm(plain_data, sizeof(plain_data), cipher_data,
				iv, sizeof(iv),
				aad, sizeof(aad),
				tag, sizeof(tag),
				aes_key, AES_KEY_LEN128,
				ICA_ENCRYPT);

	/* Error handling (if necessary). */
	if (rc)
		return handle_ica_error(rc);

	/* Dump encrypted data.
	 */
	printf("encrypted data:\n");
	dump_data(cipher_data, sizeof(plain_data));
	printf("Authetication code:\n");
	dump_data(tag, sizeof(tag));

	/* GCM解密,将cipher data解密到decrypted data.
	 * Note: 跟GCM加密必须使用相同的AES key, IV and AAD.
	 * tag消息验证码用于认证校验解密后的decrypt_data和aad变量是否一致.
	 * 如消息验证码tag认证不通过, 将返回EFAULT.
	 */
	rc = ica_aes_gcm(decrypt_data, sizeof(plain_data), cipher_data,
				iv, sizeof(iv),
				aad, sizeof(aad),
				tag, sizeof(tag),
				aes_key, AES_KEY_LEN128,
				ICA_DECRYPT);

	/* Error handling (if necessary). */
	if (rc)
		return handle_ica_error(rc);

	/* Dump decrypted data.
	 * Note: Please compare output with the plain data, they are the same.
	 */
	printf("decrypted data:\n");
	dump_data(decrypt_data, sizeof(plain_data));

	/* Surprise... :-)
	 * Note: The following will only work in this example!
	 */
	printf("%s\n", decrypt_data);
}

static void dump_data(unsigned char *data, unsigned long length)
{
	unsigned char *ptr;
	int i;

	for (ptr = data, i = 1; ptr < (data+length); ptr++, i++) {
		printf("0x%02x ", *ptr);
		if ((i % AES_CIPHER_BLOCK_SIZE) == 0)
			printf("\n");
	}
	if (i % AES_CIPHER_BLOCK_SIZE)
		printf("\n");
}

static int handle_ica_error(int rc)
{
	switch (rc) {
	case 0:
		printf("OK\n");
		break;
	case EINVAL:
		printf("Incorrect parameter.\n");
		break;
	case EPERM:
		printf("Operation not permitted by Hardware (CPACF).\n");
		break;
	case EIO:
		printf("I/O error.\n");
		break;
	case EFAULT:
		printf("The verification of the message authentication code has failed.\n");
		break;
	default:
		printf("unknown error.\n");
	}

	return rc;
}