There are three possibilities to easily execute the side-channel attack against the hybrid encryption protocol.
Possibility A:
Open the (decrypted) file "letterFromAliceToBob-DECRYPTED-en.txt" which is contained in the CrypTool package and start the side-channel attack. After closing the "Preparations" dialog choose the option "You hybrid encrypt the opened document".
Possibility B:
Open the (hybrid encrypted) file "letterFromAliceToBob-ENCRYPTED-en.hex" which is contained in the CrypTool package and start the side-channel attack. After closing the "Preparations" dialog choose the option "You use the opened document".
Possibility C:
Irrespective from which document was opened at the beginning of the side-channel attack, you can always choose the option "You use a document integrated in CrypTool..." after closing the "Preparations" dialog. Thus CrypTool is using the correct file (the hybrid encrypted file "letterFromAliceToBob-ENCRYPTED-en.hex" from option B) "in the background".
Remark 1:
The PIN for Bob's private key is always 1234.
Remark 2:
Bob needs to verify whether he could correctly decrypt received messages in order to make the side-channel attack work.
At present all messages containing the string "Alice" are correctly decrypted -- we refer to this as "keyword". One could also implement it using the entropy of the received document.
You can arbitrarily change the keyword via the CrypTool dialog "Options \ Further Options".
Please note: If you change the keyword, possibilites B and C (see above) do no longer work! In these cases the hard-coded keyword ("Alice") would not be recognized.