Add SM4 demos

demos/sm4/sm4_cbc_demo.c

@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <gmssl/sm4.h>
+#include <gmssl/rand.h>
+
+
+int main(void)
+{
+	SM4_KEY sm4_key;
+	unsigned char key[16];
+	unsigned char iv[16];
+	unsigned char mbuf[32] = {
+		0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,
+		0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,
+		0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,
+		0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,
+	};
+	unsigned char cbuf[32] = {0};
+	unsigned char pbuf[32] = {0};
+	int i;
+
+	rand_bytes(key, sizeof(key));
+	rand_bytes(iv, sizeof(iv));
+
+	printf("key: ");
+	for (i = 0; i < sizeof(key); i++) {
+		printf("%02X", key[i]);
+	}
+	printf("\n");
+
+	printf("iv: ");
+	for (i = 0; i < sizeof(iv); i++) {
+		printf("%02X", iv[i]);
+	}
+	printf("\n");
+
+	printf("plaintext: ");
+	for (i = 0; i < sizeof(mbuf); i++) {
+		printf("%02X", mbuf[i]);
+	}
+	printf("\n");
+
+	sm4_set_encrypt_key(&sm4_key, key);
+	sm4_cbc_encrypt(&sm4_key, iv, mbuf, sizeof(mbuf)/SM4_BLOCK_SIZE, cbuf);
+
+	printf("ciphertext: ");
+	for (i = 0; i < sizeof(cbuf); i++) {
+		printf("%02X", cbuf[i]);
+	}
+	printf("\n");
+
+	sm4_set_decrypt_key(&sm4_key, key);
+	sm4_cbc_decrypt(&sm4_key, iv, cbuf, sizeof(cbuf)/SM4_BLOCK_SIZE, pbuf);
+
+	printf("decrypted: ");
+	for (i = 0; i < sizeof(pbuf); i++) {
+		printf("%02X", pbuf[i]);
+	}
+	printf("\n");
+
+	return 0;
+}