Certified Ethical Hacking-Module 20 Cryptography

1. Cryptography
Cryptography: Cryptography is a technique of encrypting the clear text into scrambled code
This encrypted data is sent over public or private network toward destination to ensure confidentiality
The encrypted data is known as cipher text
Cryptanalysis: Study & methods used to crack cipher text
Objectives of Cryptography:
-Confidentiality
-Integrity
-Authentication
-Non Repudiation
Reviewer:-Raghul Prepared by:-Sandesh S M

2. Types Of Cryptography
• Symmetric Cryptography
-Uses the same secret key for encryption & decryption of data
-Most Widely Used symmetric ciphers are AES & DES
-Suitable for large amounts of data
-128 bit or larger symmetric keys are common
-Can be very fast to use
Disadvantage of symmetric cryptography
-Not scalable
-Non repudiation is possible because everyone has copy of key
-Key must be regenerated when anyone leaves the group of keyholders
• Asymmetric Cryptography
-Two keys are used
-Public Key available for anyone
-Private key is kept secret
-Also know as public key cryptography
-RSA,DSA & Diffie-Hellman algorithm are popular examples of asymmetric ciphers
-Delivers Confidentiality,Integrity,Autenticity & non repudiation
Disadvantage of Asymmetric Cryptography
-Slow in processing & requires high processing power
-Can’t be decrypted if private key is lost
Reviewer:-Raghul Prepared by:-Sandesh S M

3. Cryptosystem or Cipher System
A Cryptosystem is an implementation of cryptographic techniques & their accompanying infrastructure to
provide information security services.
A crypto system is referred to as cipher system
Defines key properties,communication requirements for the key exchange,Actions through encryption &
decryption process
Symmetric Cryptosystems:
Reviewer:-Raghul Prepared by:-Sandesh S M

4. Types of Ciphers

5. Hashes
• Process of transforming any given key or string of characters into another value
• One way Encryption
• Verify the integrity of the message
• Verifies Authenticity of message(Proof of origin & non repudiation)
• Impossible to recover the original message
• Used to store passwords using confidentiality
• Message Digest(One way Hash )Functions:
Reviewer:-Raghul Prepared by:-Sandesh S M

6. Hashing Algorithms
• MD5-Message Digest Function
-First Published in April 1992
-Replaced MD4
-Produces 128 bit Hash value
• SHA-Secure hash Algorithm
-Developed by NSA
-Widely Used
-Produces 160-bit Hashing
• SHA 2-Secure Hash Algorithm 2
-Option to vary digest between 224 bits to 512 bits
-Includes SHA-256,SHA-384 & SHA-512
• SHA 3-Secure Hash Algorithm 3
-Uses Hash function keccack
-Replaced by SHA 1 & SHA 2

7. Hash message Authentication Code-HMAC

8. Public Key Infrastructure-PKI

9. Digital Certificates

10. Encrypted Communication

11. Cryptography Attacks