有人能告诉我为什么我的密码有效，但我的密码无效吗？看照片b

Question

#维格纳密码 EncryptedMessage=“” 模式=“” Keywordcount=0#将所有内容设置为0

while Mode != "encrypt" and Mode != "decrypt":
    Mode = input('Do you want to encrypt or decrypt a message?')
    Mode = Mode.lower()

if Mode == "encrypt":

    Keyword=input('Please enter the keyword you want to use:')

    Message=input('Please eneter the message you witsh to encrypt: ')

    Keywordlength = len(Keyword)

    for i in range(0, len(Message)):#

            Messageencrypt = Message[i]
            Keywordencrypt = Keyword[Keywordcount]

            if Messageencrypt.isalpha():

                if Messageencrypt.isupper():

                    Messageencrypt = ord(Messageencrypt)

                    Keywordencrypt = Keywordencrypt.upper()

                    Keywordencrypt = ord(Keywordencrypt) - 64

                    CodedMessage = Messageencrypt + Keywordencrypt

                    if CodedMessage > 90:
                        CodedMessage = CodedMessage - 26

                    Encryptedletter = chr(CodedMessage)          


                elif Messageencrypt.islower():

                    Messageencrypt = ord(Messageencrypt)

                    Keywordencrypt = Keywordencrypt.upper()

                    Keywordencrypt = ord(Keywordencrypt) - 64

                    CodedMessage = Messageencrypt + Keywordencrypt

                    if CodedMessage > 122:
                        CodedMessage = CodedMessage - 26


                Encryptedletter = chr(CodedMessage)

            else:
                Encryptedletter = Messageencrypt

            EncryptedMessage = EncryptedMessage + Encryptedletter

            Keywordcount = Keywordcount + 1

            if Keywordcount >= Keywordlength:
                Keywordcount = 0

    print(EncryptedMessage)


if Mode == "decrypt":

    Keyword=input('Please enter the keyword you want to use:')

    Message=input('Please eneter the message you witsh to decrypt: ')

    Keywordlength = len(Keyword)

    for i in range(0, len(Message)):#

            Messageencrypt = Message[i]
            Keywordencrypt = Keyword[Keywordcount]

            if Messageencrypt.isalpha():

                if Messageencrypt.isupper():

                    Messageencrypt = ord(Messageencrypt)

                    Keywordencrypt = Keywordencrypt.upper()

                    Keywordencrypt = ord(Keywordencrypt) - 64

                    CodedMessage = Messageencrypt - Keywordencrypt

                    if CodedMessage > 90:
                        CodedMessage = CodedMessage - 26

                    Encryptedletter = chr(CodedMessage)          


                elif Messageencrypt.islower():

                    Messageencrypt = ord(Messageencrypt)

                    Keywordencrypt = Keywordencrypt.upper()

                    Keywordencrypt = ord(Keywordencrypt) - 64

                    CodedMessage = Messageencrypt - Keywordencrypt

                    if CodedMessage > 122:
                        CodedMessage = CodedMessage - 26


                Encryptedletter = chr(CodedMessage)

            else:
                Encryptedletter = Messageencrypt

            EncryptedMessage = EncryptedMessage + Encryptedletter

            Keywordcount = Keywordcount + 1

            if Keywordcount >= Keywordlength:
                Keywordcount = 0

    print(EncryptedMessage)

程序正确加密但不正确解密 有人来解释什么不对

This image show what is what happens when i try to decrypt

Answer 1

您正在加密和解密中对CodedMessage变量使用上限检查（即if CodedMessage > 90:）。这适用于encrypt，因为您希望编码的消息ASCII十进制代码大于原来的值，因为您正在添加keyencrypt。但是，对于解密，您不是在添加密钥，而是在减去密钥：

CodedMessage = Messageencrypt - Keywordencrypt

这意味着您现在期望CodedMessage比以前小，这使得更高的界限检查没有用。然后可以将代码更改为：

if CodedMessage < 65: #for upper letters
if CodedMessage < 97: #for lower letters