Basic Concept Of PKI

Why pki

Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information. A loss of confidentiality is the unauthorized disclosure of information.

Confidentiality

Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity. A loss of integrity is the unauthorized modification or destruction of information.

Integrity

Ensuring timely and reliable access to and use of information. A loss of availability is the disruption of access to or use of information or an information system.

CIA triad to define security objectives.

Availability

Cryptography is the science of writing in secret code.

The first documented use of cryptography in writing dates back to circa 1900 B.C.

New forms of cryptography came soon after the widespread development of computer communications.

In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet.

THE PURPOSE OF CRYPTOGRAPHY

Authentication: The process of proving one's identity. (The primary forms of host-to-host authentication on the Internet today are name-based or address-based, both of which are notoriously weak.)

Privacy/confidentiality: Ensuring that no one can read the message except the intended receiver.

Integrity: Assuring the receiver that the received message has not been altered in any way from the original.

Non-repudiation: A mechanism to prove that the sender really sent this message.

For Application-To-Application Communication ,Security Requirement

We will discussed three type of Cryptographic algorithms

1 Secret key cryptographic 2 Public key cryptographic 3 Hash function

TYPES OF CRYPTOGRAPHIC ALGORITHMS

objective to recover key not just message general approaches:

◦ cryptanalytic attack◦ brute-force attack

if either succeed all key use compromised

Cryptanalysis

always possible to simply try every key most basic attack, proportional to key size assume either know / recognise plaintext

Brute Force Search

Key Size (bits) Number of Alternative Keys

Time required at 1 decryption/µs

Time required at 106 decryptions/µs

32 232 = 4.3 109 231 µs = 35.8 minutes

2.15 milliseconds

56 256 = 7.2 1016 255 µs = 1142 years 10.01 hours

128 2128 = 3.4 1038 2127 µs = 5.4 1024 years

5.4 1018 years

168 2168 = 3.7 1050 2167 µs = 5.9 1036 years

5.9 1030 years

26 characters (permutation)

26! = 4 1026 2 1026 µs = 6.4 1012 years

6.4 106 years