Page 188 - DCAP516_COMPUTER_SECURITY

Computer Security

Notes 14.6.3 Message Formats

RFC 822
It is an old standard, and does not clearly distinguish envelope from header fields.
In normal usage, the user agent builds a message and passes it to the message transfer agent,
which then uses some of the header fields to construct the actual envelope.

Figure 14.4: RFC 822 Header Fields related to Message Transport

Figure 14.5: Some fields used in RFC 822 Message Format

Header Meaning
Date: The date and time the message was sent
Reply-To: E-mail address to which replies should be sent
Message-Id: Unique number for referencing this message later
In-Reply-To: Message-Id of the message to which this is a reply
References: Other relevant Message-Ids
Keywords: User-choosen keywords
Subject: Short summary of the message for the one-line display

14.6.4 Ensuring Network Security

1. How to ensure that nobody else reads your mail?
2. How to be sure that the mail has not been seen by someone else in your name?
3. Integrity i.e. mail has not been tampered with third person?

4. Non-Reputability- means once I send a mail I cannot deny it, and this fact can be proved to
a third person.
5. Authentication

14.6.5 Mechanisms

PGP (Pretty Good Privacy)

It uses some cryptography algorithm to crypt the messages. There are two types of PGP namely:

1. Symmetric PGP: the key used for encryption and decryption is the same. Example of
Symmetric PGP is DES, IDEA

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