Domino supports encryption and electronic signing of documents. VisualAge Smalltalk Domino Connection provides protocols to handle these functions with instances of the class AbtLnNote. At the end of his section, there is a sample application which explains how to sign and encrypt a document.
When you sign a document using your Notes client, a unique portion of your user ID is attached to the signed note to identify you as author. Only new documents can be signed and the signature cannot be removed once the note is stored. Signing is especially valuable with documents to be mailed.
To sign an AbtLnNote, use the sign method. The signature will be included, but the document is not actually signed until it is stored. A document which receives the sign message can be unsigned with the unsign method so long as it was not stored.
Encryption is possible on a field level. You can encrypt some or all of the fields in a document. To have a document encrypted you have to perform two steps: prepare the fields you want to encrypt by sending the prepareForEncryptionItemNamed: method for each field you want to be protected. Then send the encrypt: message with the name of one of your encryption keys as a parameter. When you store the document, the selected fields will be encrypted.
When you receive a mail document, it can be encrypted. When you try to access encrypted data, you will raise an exception. To prevent this, you might send the isEncrypted message to a document and, in case you receive a true object, you might try to decrypt the document using the decrypt method. Decrypt will try to decode the encrypted data using the decryption key included in your ID file. If you do not have the appropriate keys, the message send will raise an exception.