Front cover - IBM Redbooks

424 Lotus Security Handbook
database, as it assures that the document is authentic and was not tampered
with in any way by anyone). In addition, digital signatures ensure that the
message signer (or the document author) cannot say they did not send the
message (or write the document). This is referred to as “non-repudiation.”
Like encryption, the digital signature process is essentially transparent to the
user. Digital signatures (for e-mails, in this example), work in the following
manner:
1. The sender's e-mail client computes a message digest of the entire message.
A message digest is a one-way hash of the entire message that results in a
unique fixed-length hash of the message (regardless of the message's actual
length).
2. The sender's e-mail client encrypts the message digest using the sender's
private key, and then attaches both the encrypted message digest and the
sender's certificate (which provides the public key) to the message.
3. The recipient's e-mail client decrypts the message digest using the signer's
public key, which is part of the signer's certificate.
4. The recipient's e-mail client computes its own message digest, and compares
it with the one attached to the e-mail. If the two message digests are identical,
the message is assured to be from the sender and unaltered in transit.
Access control
Every database includes an access control list (ACL) which Domino uses to
determine the level of access that users and servers have to that database.
When a user opens a database, Domino classifies the user according to an
access level that determines privileges. The access level for a user may vary in
different databases.
The access level assigned to a user determines the tasks that the user can
perform in the database. The access level assigned to a server determines what
information the server can replicate within a particular database. Only someone
with Manager access can create or modify the ACL of a database located on a
server.
Access control levels include, from least to most permissive: No Access,
Depositor, Reader, Author, Editor, Designer, Manager.
Execution control
The ECL, introduced in Notes 4.5, enables users to protect their data against the
threats of e-mail bombs, viruses, Trojan horses, and unwanted application
intrusions. The ECL provides a mechanism for managing whether such