AES密钥扩展

Intel AES-NI 指令集为 AES 密钥扩展提供了几个重要的 intrinsic 函数

// 核心密钥扩展函数
__m128i _mm_aeskeygenassist_si128(__m128i key, int round_constant);
// 加密相关指令
__m128i _mm_aesenc_si128(__m128i state, __m128i round_key);
__m128i _mm_aesenclast_si128(__m128i state, __m128i round_key);
__m128i _mm_aesdec_si128(__m128i state, __m128i round_key);
// 解密相关指令
__m128i _mm_aesdec_si128(__m128i state, __m128i round_key);
__m128i _mm_aesdeclast_si128(__m128i state, __m128i round_key);
// 逆向密钥扩展
__m128i _mm_aesimc_si128(__m128i round_key);

1. 核心密钥扩展函数

1.1. _mm_aeskeygenassist_si128

__m128i _mm_aeskeygenassist_si128(__m128i key, int round_constant);

2. 加密相关指令

2.1. _mm_aesenc_si128

__m128i _mm_aesenc_si128(__m128i state, __m128i round_key);

2.2. _mm_aesenclast_si128

__m128i _mm_aesenclast_si128(__m128i state, __m128i round_key);

2.3. _mm_aesdec_si128

__m128i _mm_aesdec_si128(__m128i state, __m128i round_key);

3. 解密相关指令

3.1. _mm_aesdec_si128

__m128i _mm_aesdec_si128(__m128i state, __m128i round_key);

3.2. _mm_aesdeclast_si128

__m128i _mm_aesdeclast_si128(__m128i state, __m128i round_key);

4. 逆向密钥扩展

4.1. _mm_aesimc_si128

__m128i _mm_aesimc_si128(__m128i round_key);

5. 密钥扩展示例

#include <wmmintrin.h>
#include <emmintrin.h>

void aes128_key_expansion(const unsigned char* user_key, unsigned char* key_schedule) {
    __m128i key = _mm_loadu_si128((const __m128i*)user_key);
    __m128i temp;
    int i;

    // 存储初始密钥
    _mm_storeu_si128((__m128i*)key_schedule, key);

    // 生成10轮密钥（AES-128）
    for (i = 0; i < 10; i++) {
        temp = _mm_aeskeygenassist_si128(key, 0x01 << i);
        // 这里需要配合移位操作完成完整密钥扩展
        key = _mm_xor_si128(key, _mm_slli_si128(temp, 4));
        key = _mm_xor_si128(key, _mm_slli_si128(temp, 8));
        key = _mm_xor_si128(key, _mm_slli_si128(temp, 12));

        _mm_storeu_si128((__m128i*)(key_schedule + (i+1)*16), key);
    }
}

void aes128_dec_key_expansion(const unsigned char* encrypt_keys,
                             unsigned char* decrypt_keys) {
    // 存储最后一轮密钥（不变）
    _mm_storeu_si128((__m128i*)decrypt_keys, 
                    _mm_loadu_si128((const __m128i*)(encrypt_keys + 10*16)));

    // 转换其他轮密钥用于解密
    for (int i = 1; i < 10; i++) {
        _mm_storeu_si128((__m128i*)(decrypt_keys + i*16),
                        _mm_aesimc_si128(_mm_loadu_si128(
                            (const __m128i*)(encrypt_keys + (10-i)*16))));
    }

    // 存储初始密钥
    _mm_storeu_si128((__m128i*)(decrypt_keys + 10*16),
                    _mm_loadu_si128((const __m128i*)encrypt_keys));
}