Ans :
Digital Signature
Digital signature authenticates the identity of the sender of a message or signature holder
of the document. It ensures that the contents of the message are intact. The sender cannot
repudiate it later on. Digital Signatures are easily transportable. They cannot be imitated.
They can be automatically time stamped.
As per Information Technology Act, 2000, Digital Signature may be defined as
authentication of any electronic record by a subscriber by means of an electronic method or procedure in accordance with the provision of concerned sections of the Act.
IT Act provides the conditions subject to whom any electronic record(s) may be
authenticated by means of affixing digital signature.
TCS, Safes crypt and MTNL are some of the digital signature certifying authorities in
India licensed by the Controller of Certifying Authorities, Government of India.
The following are various steps in the working of a digital signature:
(a) Sender creates the message (electronic record).
(b) Electronic record is converted into message digest by using a mathematical
function known as hash function (which freezes the message).
(c) The message digest is encrypted with the sender’s private key.
(d) Sender sends the message.
(e) Receiver receives the message.
(t) Receiver decrypts the message by the sender’s public key.
(g) Receiver verifies the message.
Firewalls
Firewall is a hardware or software based security system that filters the packets and
prevents some packets from entering the network based on a security policy. A firewall
allows to establish certain rules to determine what traffic should be allowed in or out of
the private network. All data entering or leaving the Intranet pass through the firewall,
which examines each packet and blocks those that do not meet the specified security
criteria. It acts as a gatekeeper and protects a computer network from unauthorized and
malicious access.
A firewall may be hardware or software or both.
• Hardware firewalls can be found in broadband routers and is an important
part of network setup. It protects Computer on the local network. Software
firewalls are installed on the Computer and can be customized to incorporate
protection features.
The following are four mechanisms used by firewalls (refer to Table 6.2):
• Packet filter firewalls
• Stateful inspection firewalls-
• Proxy server firewalls, and
• Application level firewalls.
| Basis | Packet Filter Firewalls | Stateful Inspection Firewalls | Proxy Server Firewalls | Application Level Firewalls |
| Evaluation | Evaluates the headers of incoming and outgoing packets | Evaluates the state of TCP connection. | Act as intermediary between internal and external IP addresses &blocks direct access to internal network | Include filtering capabilities and additional validation of packet content based on the application |
| Usage | Used in small office/home office(SOHO) and operating system | Inbound network traffic | Domain name servers, mail servers and web servers | Telnet, FTP, and HTTP |
| Advantages | Faster performance than application firewalls. Effective and transparent to users. | Faster performance than application firewalls | Effectively hides true network addresses | Packets are evaluated completely. |
| Disadvantages | Does not support advanced user authentication | More complex than other firewalls, and incompatible with some protocols | Incompatible with all network protocols, and configuring these proxies is difficult | Time taken for evaluating each packet slows network traffic, and limited support for new network applications is provided |
In practice, many firewalls use two or more of these techniques in concert. A
frrewall is considered as first line of defense in protecting private information. For
greater security, data can be encrypted.·
