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用vb实现DES加解密算法(三)--解密 |
热 ★★★★ |
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用vb实现DES加解密算法(三)--解密 |
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作者:闵涛 文章来源:闵涛的学习笔记 点击数:3946 更新时间:2009/4/23 18:59:36 |
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''''进行第三次迭代 For i = 0 To 47 CodeE(i) = R2(E(i)) ''''经过E变换扩充,由32位变为48位 CodeE(i) = CodeE(i) Xor K14(i) ''''与K14按位作不进位加法运算 Next ''''分8组 For i = 0 To 5 CodeS1(i) = CodeE(i) CodeS2(i) = CodeE(i + 6) CodeS3(i) = CodeE(i + 12) CodeS4(i) = CodeE(i + 18) CodeS5(i) = CodeE(i + 24) CodeS6(i) = CodeE(i + 30) CodeS7(i) = CodeE(i + 36) CodeS8(i) = CodeE(i + 42) Next ''''S盒运算,得到8个数 S(0) = S1(CodeS1(5) + CodeS1(0) * 2, CodeS1(4) + CodeS1(3) * 2 + CodeS1(2) * 4 + CodeS1(1) * 8) S(1) = S2(CodeS2(5) + CodeS2(0) * 2, CodeS2(4) + CodeS2(3) * 2 + CodeS2(2) * 4 + CodeS2(1) * 8) S(2) = S3(CodeS3(5) + CodeS3(0) * 2, CodeS3(4) + CodeS3(3) * 2 + CodeS3(2) * 4 + CodeS3(1) * 8) S(3) = S4(CodeS4(5) + CodeS4(0) * 2, CodeS4(4) + CodeS4(3) * 2 + CodeS4(2) * 4 + CodeS4(1) * 8) S(4) = S5(CodeS5(5) + CodeS5(0) * 2, CodeS5(4) + CodeS5(3) * 2 + CodeS5(2) * 4 + CodeS5(1) * 8) S(5) = S6(CodeS6(5) + CodeS6(0) * 2, CodeS6(4) + CodeS6(3) * 2 + CodeS6(2) * 4 + CodeS6(1) * 8) S(6) = S7(CodeS7(5) + CodeS7(0) * 2, CodeS7(4) + CodeS7(3) * 2 + CodeS7(2) * 4 + CodeS7(1) * 8) S(7) = S8(CodeS8(5) + CodeS8(0) * 2, CodeS8(4) + CodeS8(3) * 2 + CodeS8(2) * 4 + CodeS8(1) * 8) ''''S盒运算32位结果 For i = 0 To 7 RetS(i * 4 + 0) = (S(i) And &H8) \ &H8 RetS(i * 4 + 1) = (S(i) And &H4) \ &H4 RetS(i * 4 + 2) = (S(i) And &H2) \ &H2 RetS(i * 4 + 3) = (S(i) And &H1) \ &H1 Next For i = 0 To 31 ''''P变换 CodeP(i) = RetS(P(i)) ''''产生L3,R3 R3(i) = L2(i) Xor CodeP(i) L3(i) = R2(i) Next ''''进行第四次迭代 For i = 0 To 47 CodeE(i) = R3(E(i)) ''''经过E变换扩充,由32位变为48位 CodeE(i) = CodeE(i) Xor K13(i) ''''与K13按位作不进位加法运算 Next ''''分8组 For i = 0 To 5 CodeS1(i) = CodeE(i) CodeS2(i) = CodeE(i + 6) CodeS3(i) = CodeE(i + 12) CodeS4(i) = CodeE(i + 18) CodeS5(i) = CodeE(i + 24) CodeS6(i) = CodeE(i + 30) CodeS7(i) = CodeE(i + 36) CodeS8(i) = CodeE(i + 42) Next ''''S盒运算,得到8个数 S(0) = S1(CodeS1(5) + CodeS1(0) * 2, CodeS1(4) + CodeS1(3) * 2 + CodeS1(2) * 4 + CodeS1(1) * 8) S(1) = S2(CodeS2(5) + CodeS2(0) * 2, CodeS2(4) + CodeS2(3) * 2 + CodeS2(2) * 4 + CodeS2(1) * 8) S(2) = S3(CodeS3(5) + CodeS3(0) * 2, CodeS3(4) + CodeS3(3) * 2 + CodeS3(2) * 4 + CodeS3(1) * 8) S(3) = S4(CodeS4(5) + CodeS4(0) * 2, CodeS4(4) + CodeS4(3) * 2 + CodeS4(2) * 4 + CodeS4(1) * 8) S(4) = S5(CodeS5(5) + CodeS5(0) * 2, CodeS5(4) + CodeS5(3) * 2 + CodeS5(2) * 4 + CodeS5(1) * 8) S(5) = S6(CodeS6(5) + CodeS6(0) * 2, CodeS6(4) + CodeS6(3) * 2 + CodeS6(2) * 4 + CodeS6(1) * 8) S(6) = S7(CodeS7(5) + CodeS7(0) * 2, CodeS7(4) + CodeS7(3) * 2 + CodeS7(2) * 4 + CodeS7(1) * 8) S(7) = S8(CodeS8(5) + CodeS8(0) * 2, CodeS8(4) + CodeS8(3) * 2 + CodeS8(2) * 4 + CodeS8(1) * 8) ''''S盒运算32位结果 For i = 0 To 7 RetS(i * 4 + 0) = (S(i) And &H8) \ &H8 RetS(i * 4 + 1) = (S(i) And &H4) \ &H4 RetS(i * 4 + 2) = (S(i) And &H2) \ &H2 RetS(i * 4 + 3) = (S(i) And &H1) \ &H1 Next For i = 0 To 31 ''''P变换 CodeP(i) = RetS(P(i)) ''''产生L4,R4 R4(i) = L3(i) Xor CodeP(i) L4(i) = R3(i) Next ''''进行第五次迭代 For i = 0 To 47 CodeE(i) = R4(E(i)) ''''经过E变换扩充,由32位变为48位 CodeE(i) = CodeE(i) Xor K12(i) ''''与K12按位作不进位加法运算 Next ''''分8组 For i = 0 To 5 CodeS1(i) = CodeE(i) CodeS2(i) = CodeE(i + 6) CodeS3(i) = CodeE(i + 12) CodeS4(i) = CodeE(i + 18) CodeS5(i) = CodeE(i + 24) CodeS6(i) = CodeE(i + 30) CodeS7(i) = CodeE(i + 36) CodeS8(i) = CodeE(i + 42) Next ''''S盒运算,得到8个数 S(0) = S1(CodeS1(5) + CodeS1(0) * 2, CodeS1(4) + CodeS1(3) * 2 + CodeS1(2) * 4 + CodeS1(1) * 8) S(1) = S2(CodeS2(5) + CodeS2(0) * 2, CodeS2(4) + CodeS2(3) * 2 + CodeS2(2) * 4 + CodeS2(1) * 8) S(2) = S3(CodeS3(5) + CodeS3(0) * 2, CodeS3(4) + CodeS3(3) * 2 + CodeS3(2) * 4 + CodeS3(1) * 8) S(3) = S4(CodeS4(5) + CodeS4(0) * 2, CodeS4(4) + CodeS4(3) * 2 + CodeS4(2) * 4 + CodeS4(1) * 8) S(4) = S5(CodeS5(5) + CodeS5(0) * 2, CodeS5(4) + CodeS5(3) * 2 + CodeS5(2) * 4 + CodeS5(1) * 8) S(5) = S6(CodeS6(5) + CodeS6(0) * 2, CodeS6(4) + CodeS6(3) * 2 + CodeS6(2) * 4 + CodeS6(1) * 8) S(6) = S7(CodeS7(5) + CodeS7(0) * 2, CodeS7(4) + CodeS7(3) * 2 + CodeS7(2) * 4 + CodeS7(1) * 8) S(7) = S8(CodeS8(5) + CodeS8(0) * 2, CodeS8(4) + CodeS8(3) * 2 + CodeS8(2) * 4 + CodeS8(1) * 8) ''''S盒运算32位结果 For i = 0 To 7 RetS(i * 4 + 0) = (S(i) And &H8) \ &H8 RetS(i * 4 + 1) = (S(i) And &H4) \ &H4 RetS(i * 4 + 2) = (S(i) And &H2) \ &H2 RetS(i * 4 + 3) = (S(i) And &H1) \ &H1 Next For i = 0 To 31 ''''P变换 CodeP(i) = RetS(P(i)) ''''产生L5,R5 R5(i) = L4(i) Xor CodeP(i) L5(i) = R4(i) Next 上一页 [1] [2] [3] [4] [5] [6] [7] [8] 下一页 没有相关教程
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