SChatBUDDY Tutorial

I believe there is no need for a documentation about SChatBUDDY because the software is quite self-explanatory. Nevertheless, here are some basics.

SChatBUDDY encrypts and decrypts data to and from a chat partner. This partner is identified by his key.

Before starting an encrypted chat session keys must be created and exchanged. In case of a symmetric key, one of the partners must create the key and send it to the other partner, who has to store it. As you may notice, the use of symmetric keys has a drawback: the key can not be sent in a secure channel, because for encryption, both sides always have to have the key!

Therefore SChatBUDDY 3.0 implements public/private key pairs. Each chat partner creates a public/private key pair, and sends the public part of the key pair to the other partner. The public part of the key pair is enough for someone to encrypt a message, and as the public key does not contain any information about the private key, the public key exchange is secure. To communicate with multiple chat partners you only need one public key. Because the encryped message uses your private key and the chat partner's public key, the message can only be decrypted be the person you sent it to.

SChatBUDDY stores keys in a secure (encrypted) keyring (menu option “Key Management”). A key is attached to a session ID (for example the name of the chat partner). Once in the “Key Management” screen use the popup menu to add/remove session keys.

Figure 1: Key management screen

The key creation wizard (Figure 2) allows the creation of symmetric and asymmetric keys, and the import of other partie's public keys.

Figure 2: the Key Creation Wizard

Once keys created and exchanged, a secure chat session can be started. SChatBUDDY offers Clipboard support for encryption and decryption.

To encrypt a text, select the cleartext to encrypt, and the select “Encrypt Clipboard” from the SChatBUDDY tray icon. The partner selection dialog appears (Figure 3).

Figure 3: Select session partner

When the partner key has been selected the clipboard is encrypted with the corresponding key, and the result (ciphertext) is placed in the clipboard. It is ready to be pasted in your favorite chat program.

To decrypt a message, the ciphertext has first to be placed in the clipboard. The selection the “Decrypt Clipboard” from the Tray Icon. The decrypted message and the sender are displayes (Firgure 4).

Figure 4: Decrypting a message

The way SChatBUDDY handles messages can be set in the preferences. There are different options, for different function groups:

The option “Keep session label for next encryption” enables the default session label displayed in the session partner selection dialog (see Figure 3).

The option “Don't ask for session key” allows you to select the destinator key once; then all messages will be encrypted to this key, without prompt.

Figure 5: Encryption options

Two modes are available:

• Blowfish standard
• Blowfish CBC with init. vector

These settings are only for symmetric encryption. For more info, please refer to the technical notes about SChatBUDDY.

Figure 6: Symmetric encryption options

There are two ways of using public/private key encryption:

• The message is encrypted with am asymmetric algorithm
• The message is encrypted with a symmetric algorithm, and the symmetric key (session key) is encrypted with an asymetric algorithm. Please refer to the technical notes about SChatBUDDY for more info.

Figure 7: Asymetric encryption options