JBO Catflap Cipher Help

Catflap Cipher is designed to encrypt and decrypt text mesages using a unique implementation of classical methods of encryption.

Overview:

On opening the programme, the ninety-five permitted characters are displayed in the rightmost section of the status bar.
Catflap automatically removes control and extended characters from the text before encryption or decryption (if a ciphertext contains such characters then it is probably not a Catflap ciphertext). The stripped text is subjected to polyalphabetic substitution against a table of randomly generated cipher alphabets as determined by the user-entered Key Word.

Ciphertext which has been encrypted by Catflap yields Frequency Analysis and Sequence Analysis results which are very similar to those for randomly generated text. With one kilobyte or more of text, frequency is generally below 6% for all characters (subject to key words which are not overly repetitious).

Operation:

The Open, Save, Print, and Clear toolbar buttons perform those actions for the selected editor page.
A minimum of three alphabetic characters of data is required and you must set the Key before encryption or decryption is possible.
The Help page is accessible from the help menu or by pressing F1. This page auto closes when another page is selected.

Encryption:

Select the Plain Text tab to display the plaintext editor. You may load a text file into the plaintext editor, or type the message you wish to encrypt. Set the alphanumeric key - one or more characters up to the length of the plain text. Click the Encrypt button. The ciphertext is now in the Cipher Text editor.
As space characters are permitted in the plaintext, it is possible for small sequences of spaces to appear in the cipher text. For this reason, avoid using 'copy and paste' for transferring the ciphertext from the Catflap programme to its destination. It is recommended to save the ciphertext and then transfer the resulting file to the recipient by the intended means, perhaps attached to an email. Alternatively, the ciphertext can be printed directly from Catflap.

Decryption:

Select the Cipher Text tab to display the ciphertext editor. You may load a text file into the ciphertext editor, or type the message you wish to decrypt. Set the alphanumeric key - one or more characters up to the length of the plain text. Click the Decrypt button. The plaintext is now in the Plain Text editor.