The document discusses Abstract Syntax Notation (ASN.1), which defines a standard for representing and encoding data structures. It consists of an abstract syntax that describes data unambiguously and a transfer syntax that encodes objects for transmission. ASN.1 is associated with encoding rules like BER, DER, and PER. It provides an example of ASN.1 abstract syntax defining a student record. The document also discusses other related topics like XDR, data compression techniques, video compression, encryption, and security services provided by encryption.

1. Edmond Wong Sing Huat B031110038
Khor Yong Jian B031110173
Goh Zong Wei B031110071
Fairus Binti Aziz B031110326

3.  Abstract Syntax Notation (ASN.1) is an ISO
standard that addresses the issue of
representing, encoding, transmitting, and
decoding data structures. It consists of two
parts:
1. An abstract syntax that describes data structures in
an unambiguous way. Use “ integers”, “character
strings”, and “structures” rather than bits and bytes.
2. A transfer syntax that describes the bit stream
encoding of ASN.1 data objects.

4.  The main reasons for the success of ASN.1 is that
it is associated with several standardized
encoding rules such as:
◦ Basic Encoding Rules (BER) - X.209
◦ Canonical Encoding Rules (CER)
◦ Distinguished Encoding Rules (DER)
◦ Packed Encoding Rules (PER) and
◦ XER Encoding Rules (XER).
 These encoding rules describe how the values
defined in ASN.1 should be encoded for
transmission, regardless of machine,
programming language, or how it is represented in
an application program.

5. Example of ASN.1’S abstract syntax:
Student ::= SEQUENCE {
name [0] IMPLICIT OCTET STRING OPTIONAL,
grad [1] IMPLICIT BOOLEAN OPTIONAL DEFAULT
FALSE,
gpa [2] IMPLICIT REAL OPTIONAL,
id [3] IMPLICIT INTEGER,
bday [4] IMPLICIT OCTET STRING OPTIONAL
}

6. Though initially used for specifying the
email protocol within the Open Systems
Interconnection environment, ASN.1 has
since then been adopted for a wide range
of other applications, as in network
management, secure email, cellular
telephony, air traffic control, and voice and
video over the Internet.

7. Though initially used for specifying the
email protocol within the Open Systems
Interconnection environment, ASN.1 has
since then been adopted for a wide range
of other applications, as in network
management, secure email, cellular
telephony, air traffic control, and voice and
video over the Internet.

8.  Sun Microsystems's External Data
Representation (XDR) is much simpler than
ASN.1, but less powerful. For instance:
1. XDR uses implicit typing. Communicating peers
must know the type of any exchanged data. In
contrast, ASN.1 uses explicit typing; it includes
type information as part of the transfer syntax.
2. In XDR, all data is transferred in units of 4 bytes.
Numbers are transferred in network order, most
significant byte first.

9. 4 bytes of XDR message:

10. 3. Strings consist of a 4 byte length, followed by
the data (and perhaps padding in the last byte).
4. Defined types include: integer, enumeration,
Boolean, floating point, fixed length array,
structures, plus others.
One advantage that XDR has over ASN.1
is that current implementations of ASN.1
execute significantly slower than XDR.

11. " The message “£100 is about !150” could
become
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=ISO-8859-
15
MIME-Version: 1.0
=A3100 is about =A4150

12. or
Content-Transfer-Encoding: base64
Content-Type: text/plain; charset=ISO-8859-
15
MIME-Version: 1.0
ozEwMCBpcyBhYm91dCCkMTUwCg=49

14. Reduces the number of bits contained in
the information.
Sometimes programs need to send more
data in a timely fashion than the bandwidth
of the network supports.
Need to compress the data at the sender
and decompress it at the receiver.

15. In terms of storage, the capacity of a
storage device can be effectively increased
with methods that compresses a body of
data.
The bandwidth of a digital communication
link can be effectively increased by
compressing data at the sending end and
decompressing data at the receiving end.

16. Lossless Compression – data is
compressed and can be uncompressed
without loss of information. These are
referred to as bit-preserving or reversible
compression systems.
Lossy Compression – aim to obtain the
best possible fidelity for a given bit-rate or
minimizing the bit-rate to achieve a given
fidelity measure. Most suited to video and
audio compression techniques

17. Lossless
- Image quality is not reduced.
Use in: artificial images that contain sharp-
edged lines such as technical drawings,
textual graphics, comics, maps or logos.

18.  Lossy
- reduces image quality. Cannot get the
original image back & lose some
information.
Use in: natural images such as photos of
landscapes

19.  Lossless - allows one to preserve an exact
copy of one's audio files
Usage: For archival purposes, editing,
audio quality.

20.  Lossy - irreversible changes , achieves far
greater compression, use psychoacoustics
to recognize that not all data in an audio
stream can be perceived by the human
auditory system.
Usage: distribution of streaming audio, or
interactive applications

21. • Start by encoding the first frame using a
still image compression method.
• It should then encode each successive
frame by identifying the differences
between the frame and its predecessor,
and encoding these differences. If the
frame is very different from its
predecessor it should be coded
independently of any other frame.

22. In the video compression literature, a
frame that is coded using its predecessor
is called inter frame (or just inter), while a
frame that is coded independently is called
intra frame (or just intra).

24. • To carry sensitive information, a system
must be able to assure privacy.
• One way to safeguard data from attacks
is encrypting the data.

25. • Encryption – sender transform original
information (plaintext) to another form
(ciphertext) by a function that is
parameterized by a key.
• Decryption – reverses the original
process to transform the message
(ciphertext) back to its original form
(plaintext).

26. Plaintext Plaintext
Ciphertext

27. Symmetric Keys – use same key to
encrypt and decrypt a message.

28. Asymmetric Keys -2 keys are needed
(public key and private key); 1 key to
encrypt, another key to decrypt and vice
versa.

29. Protection Description
Confidentiality Allow only authorized users to access
information.
Authentication Verify who the sender was and trust
the sender is who they claim to be.
Integrity Trust the information has not been
altered
No repudiation Ensure that the sender or receiver
cannot deny that a message was sent
or received.
Access Control Restrict availability to information.