AES 256 CTR Encryption/Decryption

最新推荐文章于 2025-05-23 17:02:32 发布

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本文深入探讨了AES 256位CTR模式的加密和解密过程，介绍了CTR模式的工作原理，以及它如何提供高效且安全的数据加密。内容包括密钥生成、初始化向量的使用以及在实际应用中的注意事项。

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struct ctr_state 
{ 
    unsigned char ivec[16]; 
    unsigned int num; 
    unsigned char ecount[16]; 
}; 

int init_ctr(struct ctr_state *state, const unsigned char iv[16])
{ 
    state->num = 0; 

    memset(state->ecount,0,16);
    memset(state->ivec + 8, 0, 8);   /* Copy IV into 'ivec' */ 
    memcpy(state->ivec, iv, 8); 

    return 0;
} 

struct ctr_state state;

void ctr_encrypt(const size_t encslength, AES_KEY key, int length) 
    {
        init_ctr(&state, iv);
        unsigned char my_data[16], output[16];

        AES_set_encrypt_key((unsigned char*)rkey, 256, &key);

        for (int i=1; i<encslength/16+1; i++)
        {
            memset(my_data,0,16);
            memcpy(my_data,plaintext+((i-1)*16),16);
            AES_ctr128_encrypt((unsigned char*)my_data, (unsigned char*)output, 16, &key, state.ivec, state.ecount, &state.num);
            memcpy(ciphertext+((i-1)*16),output,16);
        }

        hexdump(stdout, "ciphertext", (unsigned char*)ciphertext, length);
    }


    void ctr_decrypt(const size_t encslength, AES_KEY key, int length)
    {
        init_ctr(&state, iv);
        unsigned char my_data[16], output[16];

        AES_set_encrypt_key((unsigned char*)rkey, 256, &key);

        for (int i=1; i<encslength/16+1; i++)
        {
            memset(my_data,0,16);
            memcpy(my_data,ciphertext+((i-1)*16),16);
            AES_ctr128_encrypt((unsigned char*)my_data, (unsigned char*)output, 16, &key, state.ivec, state.ecount, &state.num);
            memcpy(checktext+((i-1)*16),output,16);
        }

        hexdump(stdout, "checktext", (unsigned char*)checktext, length);
    }