Dialog Key Entry: Homophonic Substitution

Dialog for the encryption algorithm Homophonic Substitution.

This dialog generates a random key for the Homophonic Substitution algorithm. In the current version of CrypTool it is not possible to enter a user defined key.

The following parameters are relevant for Homophonic Substitution keys:

After having chosen the alphabet and reference file via menu Options \ Text Options, the upper part of the dialog allows you to define the total number of homophones and whether the above formatting characters shall be encrypted or not.

The number of homophones determines bit length of the cipher text characters. For an alphabet with 1024 homophones, e. g. each clear text character is encrypted into a number from the range 0,....,1023. Each of those numbers needs 10 bits to be represented uniquely. In that case a 2000 Byte text will be expanded to a cipher text of 2000 x 10 Bit = 2500 Bytes.

On clicking the button Update

On clicking the button Generate random key a new random homophonic key is computed.

You can encrypt the document by clicking the Encrypt button or pressing the enter key.

The result of encryption is a binary file.

Before you can decrypt a binary document, you have to save the homophonic key in the Key Store (after activating the encrypted document in the CrypTool desktop you can copy the homophonic key via the menu Edit \ Show Key: in the following dialog you click Copy key). You can then insert the key into this dialog by pressing iconinsertkey.gif (this button is greyed out if no key is available). To decrypt the document click the Decrypt button.