Differential Analysis of Reduced Rounds Block Cipher LEA
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摘要: LEA算法是面向软件的轻量级加密算法,在2019年成为 ISO/IEC 国际标准轻量级加密算法,具有快速加密、占用运算资源少等优点。该文基于多条输入输出差分相同的路径计算了差分概率,首次对LEA-128进行了13轮和14轮的密钥恢复攻击;采用提前抛弃技术,分别在12轮和13轮差分特征后面添加了1轮,恢复了96 bit密钥;其中13轮的密钥恢复攻击数据复杂度为298个明文,时间复杂度为286.7次13轮LEA-128解密;14轮的密钥恢复攻击数据复杂度为2118个明文,时间复杂度为2110.6次14轮LEA-128解密。Abstract: The LEA algorithm is a software-oriented lightweight encryption algorithm, which became the ISO/IEC international standard lightweight encryption algorithm in 2019. It has the advantages of fast encryption and less computing resources. The differential probability is calculated based on multiple paths with the same input-output difference, 13 and 14 rounds of key recovery attacks of LEA-128 are given for the first time. Using the early abort technology, one round is added after the 12-round and 13-round differential characteristic, and a total of 96 bit keys are recovered. The 13-round key recovery attack has a data complexity of 298 plaintext and a time complexity of 286.7 times of 13 rounds of LEA-128 decryption; the 14-round key recovery attack has a data complexity of 2118 plaintext and a time complexity of 2110.6 times of 14 rounds of LEA-128 decryption.
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Key words:
- Lightweight block cipher /
- ARX /
- Differential analysis /
- Key recovery attack
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表 1 LEA-128攻击分析结果比较
算法1 最优特征的差分概率 输入:对于 r 轮密码的原始MILP模型。 输出:最优特征的概率多项式。 (1) 求解原始MILP模型并获得最优差分特征的概率 d 和
$(\varDelta _{ {\text{in} } }^ * ,\varDelta _{ {\text{out} } }^ * )$;(2) 令 j = –1 ; (3) 重复: (4) j = j + 1 ; (5) 将原始MILP模型中的输入输出差分设为$(\varDelta _{ {\text{in} } }^ * ,\varDelta _{ {\text{out} } }^ * )$; (6) 令原始MILP模型中的目标函数 = d + j ; (7) 求解模型和不同特征的数量值$ {p_j} $;
(8) 直到${p_j}{2^{ - (d + j)} } \ge \displaystyle\sum\limits_{i = 0}^{j - 1} { {p_i}{2^{ - (d + i)} } }$;(9) 令N = j – 1; (10) 返回:概率多项式。 表 2 LEA算法的12轮差分特征及概率
轮数 $\Delta {X_0}$ $ \Delta {X_{\text{1}}} $ $\Delta {X_{\text{2}}}$ $\Delta {X_{\text{3}}}$ ${\log _2}p$ 0 C0000000 C0400080 40400010 40400012 – 1 80010000 8000000C 40000004 C0000000 –13 2 02001800 82000000 80000000 80010000 –8 3 00300100 00100000 00002000 02001800 –4 4 00020000 0001FF00 00400100 00300100 –15 5 00020000 00020000 00020000 00020000 –25 6 00000000 00000000 00000000 00020000 –5 7 00000000 00000000 00004000 00000000 –1 8 00000000 00000200 00000800 00000000 –2 9 00040000 00000030 00000100 00000000 –5 10 08002000 80000008 00000020 00040000 –7 11 00401110 C4000000 00008004 08002000 –8 12 80222188 22200400 81001400 00401110 –14 表 3 LEA算法的13轮差分特征及概率
轮数 $\Delta {X_0}$ $ \Delta {X_{\text{1}}} $ $\Delta {X_{\text{2}}}$ $\Delta {X_{\text{3}}}$ ${\log _2}p$ 0 C0000000 C0400080 40400010 40400012 – 1 80010000 8000000C 40000004 C0000000 –13 2 02001800 82000000 80000000 80010000 –8 3 00300100 00100000 00002000 02001800 –4 4 00020000 0001FF00 00400100 00300100 –15 5 00020000 00020000 00020000 00020000 –25 6 00000000 00000000 00000000 00020000 –5 7 00000000 00000000 00004000 00000000 –1 8 00000000 00000200 00000800 00000000 –2 9 00040000 00000030 00000100 00000000 –5 10 08002000 80000008 00000020 00040000 –7 11 00401110 C4000000 00008004 08002000 –8 12 80222188 22200400 81001400 00401110 –14 13 04491144 05190080 102800A1 80222088 –20 -
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