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PRESENT是一种超轻量级分组密码算法#xff0c;由Bogdanov等人在2007年提出#xff0c;专门为资源受限环境如RFID标签和传感器网络设计。该算法在硬件实现上仅需1570个门等效电路(GE)#xff0c;在保持较高安全性的同时实现了极小的硬件占用空间。PRES…一、PRESENT算法介绍
PRESENT是一种超轻量级分组密码算法由Bogdanov等人在2007年提出专门为资源受限环境如RFID标签和传感器网络设计。该算法在硬件实现上仅需1570个门等效电路(GE)在保持较高安全性的同时实现了极小的硬件占用空间。PRESENT标准文档下载地址为PRESENT: An Ultra-Lightweight Block Cipher。
PRESENT采用SPN结构分组长度为64位支持80位和128位两种密钥长度。算法包含31轮加密操作每轮由轮密钥加、S盒替换和P盒置换三个步骤组成。其中S盒是一个4位输入输出的非线性变换P盒则是一个64位的线性置换层。这种简洁的结构使得PRESENT在硬件实现上非常高效。
安全性方面PRESENT设计时充分考虑了差分分析和线性分析等攻击方法。通过理论证明任何5轮差分特征至少包含10个活跃S盒25轮差分特征的概率上限为线性分析则需约个已知明文才能成功攻击这些安全指标完全满足轻量级应用场景的需求。
二、C语言实现
我们提供的C代码完整实现了PRESENT-80算法包括加密、解密和密钥扩展功能。实现中定义了几个关键组件
首先定义了算法核心的S盒和P盒置换表。S盒是一个16元素的查找表实现非线性变换P盒则定义了64位状态的置换规则。代码中同时包含了正向和反向的S盒/P盒分别用于加密和解密过程。
present_permutation函数实现了通用的置换操作根据传入的置换规则表对输入数据进行重排。这个函数被P盒置换(PSub)和逆P盒置换(InvPSub)复用通过不同的置换规则表实现不同的置换效果。
密钥扩展部分(present_key_expansion和keyUpdate)实现了80位主密钥到32个轮密钥的派生过程。每轮密钥通过旋转、S盒变换和轮计数器异或等操作生成确保了密钥材料的充分混淆。
加密过程(present_encrypt_block)遵循算法标准结构31轮迭代处理每轮包含轮密钥加、S盒替换和P盒置换最后再进行一次轮密钥加作为后处理。解密过程(present_decrypt_block)则逆向执行这些操作。
代码中还包含了四个测试用例验证了实现与标准测试向量的正确性。这些测试用例来自于标准文档覆盖了全零、全一的明文和密钥组合能够有效验证算法的基本功能。
#includestdio.h
#includestdint.hstatic const uint8_t present_sbox[16] {0xC, 0x5, 0x6, 0xB, 0x9, 0x0, 0xA, 0xD, 0x3, 0xE, 0xF, 0x8, 0x4, 0x7, 0x1,0x2};
static const uint8_t present_inv_sbox[16] {0x5, 0xE, 0xF, 0x8, 0xC, 0x1, 0x2, 0xD, 0xB, 0x4, 0x6, 0x3, 0x0, 0x7, 0x9,0xA};static const uint8_t present_pbox[64] {0, 4, 8, 12, 16, 20, 24, 28,32, 36, 40, 44, 48, 52, 56, 60,1, 5, 9, 13, 17, 21, 25, 29,33, 37, 41, 45, 49, 53, 57, 61,2, 6, 10, 14, 18, 22, 26, 30,34, 38, 42, 46, 50, 54, 58, 62,3, 7, 11, 15, 19, 23, 27, 31,35, 39, 43, 47, 51, 55, 59, 63
};static const uint8_t present_inv_pbox[64] {0, 16, 32, 48, 1, 17, 33, 49,2, 18, 34, 50, 3, 19, 35, 51,4, 20, 36, 52, 5, 21, 37, 53,6, 22, 38, 54, 7, 23, 39, 55,8, 24, 40, 56, 9, 25, 41, 57,10, 26, 42, 58, 11, 27, 43, 59,12, 28, 44, 60, 13, 29, 45, 61,14, 30, 46, 62, 15, 31, 47, 63
};void present_permutation(const uint8_t *src, uint8_t *res, const uint8_t *rule, uint8_t len) {uint8_t dest_pos, dest_bit;for (uint8_t i 0; i len; i) {res[i] 0;for (uint8_t j 0; j 8; j) {dest_pos rule[8 * i j];dest_bit (src[dest_pos 3] (7 - (dest_pos 0x07))) 0x01;res[i] res[i] | (dest_bit (7 - j));}}
}void addRoundKey(uint8_t *state, const uint8_t *ikey, uint8_t r) {for (uint8_t i 0; i 8; i) {state[i] ^ ikey[8 * r i];}
}void SubByte(uint8_t *state) {for (int i 0; i 8; i) {uint8_t s0 present_sbox[state[i] 0xf];uint8_t s1 present_sbox[state[i] 4];state[i] s0 | s1 4;}
}void InvSubByte(uint8_t *state) {for (int i 0; i 8; i) {uint8_t s0 present_inv_sbox[state[i] 0xf];uint8_t s1 present_inv_sbox[state[i] 4];state[i] s0 | s1 4;}
}void PSub(uint8_t *state) {uint8_t tmp[8] {0};for (uint8_t i 0; i 8; i) {tmp[i] state[i];}present_permutation(tmp, state, present_pbox, 8);
}void InvPSub(uint8_t *state) {uint8_t tmp[8] {0};for (uint8_t i 0; i 8; i) {tmp[i] state[i];}present_permutation(tmp, state, present_inv_pbox, 8);
}void keyUpdate(uint8_t *key, uint8_t rc) {uint8_t k[10] {key[7] 5 | key[8] 3, key[8] 5 | key[9] 3, key[9] 5 | key[0] 3, key[0] 5 | key[1] 3,key[1] 5 | key[2] 3,key[2] 5 | key[3] 3, key[3] 5 | key[4] 3, key[4] 5 | key[5] 3, key[5] 5 | key[6] 3,key[6] 5 | key[7] 3};k[0] (k[0] 0xf) | (present_sbox[k[0] 4] 4);rc rc 0x1f;k[7] ^ rc 1;k[8] ^ rc 7;for (uint8_t i 0; i 10; i) {key[i] k[i];}
}void present_key_expansion(const uint8_t *mkey, uint8_t *ikey) {uint8_t mk[10];for (uint8_t i 0; i 10; i) {mk[i] mkey[i];ikey[i] mkey[i];}for (uint8_t i 1; i 32; i) {keyUpdate(mk, i);for (uint8_t j 0; j 8; j) {ikey[8 * i j] mk[j];}}
}void present_encrypt_block(const uint8_t *plain, uint8_t *cipher, uint8_t *ikey) {uint8_t state[8];for (uint8_t i 0; i 8; i) {state[i] plain[i];}for (int r 1; r 32; r) {addRoundKey(state, ikey, r - 1);SubByte(state);PSub(state);}addRoundKey(state, ikey, 31);for (uint8_t i 0; i 8; i) {cipher[i] state[i];}
}void present_decrypt_block(const uint8_t *cipher, uint8_t *plain, uint8_t *ikey) {uint8_t state[8];for (uint8_t i 0; i 4; i) {state[i] cipher[3 - i];state[i 4] cipher[7 - i];}for (int i 31; i 1; i--) {addRoundKey(state, ikey, i);InvPSub(state);InvSubByte(state);}addRoundKey(state, ikey, 0);for (uint8_t i 0; i 4; i) {plain[i] state[3 - i];plain[i 4] state[7 - i];}
}void print_data(uint8_t *data, int data_len, const char *name) {printf(\t%s: , name);for (int i 0; i data_len; i) {printf(%02x , data[i]);}printf(\n);
}void test_case1() {printf(test case 1:\n);uint8_t mkey[] {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};uint8_t plain[] {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};uint8_t ikey[256] {0};uint8_t cipher[8] {0};print_data(plain, 10, plaintext);print_data(mkey, 8, mkey);present_key_expansion(mkey, ikey);present_encrypt_block(plain, cipher, ikey);print_data(cipher, 8, ciphertext);
}void test_case2() {printf(test case 2:\n);uint8_t mkey[] {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};uint8_t plain[] {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};uint8_t ikey[256] {0};uint8_t cipher[8] {0};print_data(plain, 10, plaintext);print_data(mkey, 8, mkey);present_key_expansion(mkey, ikey);present_encrypt_block(plain, cipher, ikey);print_data(cipher, 8, ciphertext);
}void test_case3() {printf(test case 3:\n);uint8_t mkey[] {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};uint8_t plain[] {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};uint8_t ikey[256] {0};uint8_t cipher[8] {0};print_data(plain, 10, plaintext);print_data(mkey, 8, mkey);present_key_expansion(mkey, ikey);present_encrypt_block(plain, cipher, ikey);print_data(cipher, 8, ciphertext);
}void test_case4() {printf(test case 4:\n);uint8_t mkey[] {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};uint8_t plain[] {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};uint8_t ikey[256] {0};uint8_t cipher[8] {0};print_data(plain, 10, plaintext);print_data(mkey, 8, mkey);present_key_expansion(mkey, ikey);present_encrypt_block(plain, cipher, ikey);print_data(cipher, 8, ciphertext);
}int main() {test_case1();test_case2();test_case3();test_case4();return 0;
} 三、总结
PRESENT算法通过精心设计的简洁结构在资源受限环境中实现了安全性与效率的良好平衡。其硬件友好的特性使其成为物联网安全领域的理想选择。提供的C语言实现完整展现了算法的工作流程模块化设计清晰便于理解和移植。
这种轻量级密码算法代表了密码学在物联网时代的发展方向即在有限资源下提供足够的安全保障。随着物联网设备的普及类似PRESENT这样的高效密码算法将发挥越来越重要的作用。我们的代码实现不仅可用于学术研究也可应用于实际的嵌入式安全解决方案中。
