```python # 置换表等相关常量 ip = [58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7] # 其他置换表和函数定义 def des_encrypt(plaintext, key): # 加密流程实现 #... def des_decrypt(ciphertext, key): # 解密流程实现 #... # 测试代码 plaintext = 0x0*********abcdef key = 0x1f1f1f1f0e0e0e0e ciphertext = des_encrypt(plaintext, key) decrypted

text = des_decrypt(ciphertext, key) print("Ciphertext:", ciphertext) print("Decrypted text:", decrypted_text) ``` In the provided code snippet, there are several issues that need to be addressed for a complete and functional DES encryption/decryption implementation. Here's a step-by-step guide on how to correct and complete the code: 1. Define the Permutation Tables: The initial permutation table (`ip`) is defined correctly. However, other tables such as the expansion table, substitution boxes (S-boxes), permutation tables, and the final permutation table are also necessary. 2. Key Scheduling: DES uses a 56-bit key, which needs to be expanded into 16 subkeys of 48 bits each. This involves permutations and shifts. 3. Initial Permutation (IP): Before the main rounds, the plaintext undergoes an initial permutation. 4. Round Function: Each round includes expansion, XOR with the subkey, substitution using S-boxes, permutation, and XOR with the left half of the data block. 5. Final Permutation (FP): After all rounds, the halves are swapped and combined, then undergo a final permutation to produce the ciphertext. 6. Implementing Encryption and Decryption: The `des_encrypt` and `des_decrypt` functions should follow the steps outlined above. Here's a more complete version of the code with placeholders for missing parts: ```python # 置换表等相关常量 ip = [58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7] # 其他置换表和函数定义 # Placeholder for expansion table expansion_table = [32, 1, 2, 3, ...] # Complete this table # Placeholder for S-boxes s_boxes = [[[63, 7, 20, ...], ...], ...] # Complete these S-boxes # Placeholder for permutation table after S-box substitution p_table = [16, 7, 20, ...] # Complete this table # Placeholder for final permutation table fp = [40, 8, 48, ...] # Complete this table def key_schedule(key): # Key scheduling logic here pass def initial_permutation(data): return [data[i - 1] for i in ip] def final_permutation(data): return [data[i - 1] for i in fp] def expand(right): return [right[i - 1] for i in expansion_table] def substitute(expanded_right): # Substitution logic using S-boxes pass def permute(substituted): return [substituted[i - 1] for i in p_table] def xor(a, b): return [x ^ y for x, y in zip(a, b)] def split_block(block): left = block[:32] right = block[32:] return left, right def merge_block(left, right): return left + right def des_round(left, right, subkey): expanded_right = expand(right) xored = xor(expanded_right, subkey) substituted = substitute(xored) permuted = permute(substituted) new_right = xor(left, permuted) return right, new_right def des_encrypt(plaintext, key): subkeys = key_schedule(key) data = initial_permutation(plaintext) left, right = split_block(data) for subkey in subkeys: left, right = des_round(left, right, subkey) return final_permutation(merge_block(right, left)) def des_decrypt(ciphertext, key): subkeys = key_schedule(key) data = initial_permutation(ciphertext) left, right = split_block(data) for subkey in reversed(subkeys): left, right = des_round(left, right, subkey) return final_permutation(merge_block(right, left)) # 测试代码 plaintext = [0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef] # Example plaintext key = [0x1f, 0x1f, 0x1f, 0x1f, 0x0e, 0x0e, 0x0e, 0x0e] # Example key ciphertext = des_encrypt(plaintext, key) decrypted_text = des_decrypt(ciphertext, key) print("Ciphertext:", ciphertext) print("Decrypted text:", decrypted_text) ``` This code provides a structure for implementing DES encryption and decryption. You will need to fill in the missing parts like the expansion table, S-boxes, permutation tables, and the key schedule function. [2024-10-30 12:18:51 | AI写代码神器 | 1523点数解答]