Cryptography

Presented By:Sanjeev Kumar

Dept: I.T

Cryptography Intro

Why Encrypt?• Protect stored information

• Protect from Unauthorized disclosure

Encryption - process by which plaintext is converted to cipher text using a key

Decryption - process by which cipher text is converted to plaintext (with the appropriate key)

plaintext (clear text)- intelligible data

Cryptography Terminology

Cryptography - art/science relating to encrypting, decrypting information

Cryptanalysis - art/science relating to converting cipher text to plaintext without the (secret) key

Here we have three types of algorithms that we can talk about:

MODERN CRYPTOGHRAPHY

Secret Key Cryptography

Hash Functions

Public Key Cryptography

MODERN CRYPTOGHRAPHY

Secret key

Here we have three types of algorithms that we can talk about:

MODERN CRYPTOGHRAPHY

Secret Key Cryptography

Hash Functions

Public Key Cryptography

MODERN CRYPTOGHRAPHY

Secret key

Secret Key(Symmetric) Cryptography uses a single key for both encryption and decryption.

SECRET KEY CRYPTOGHRAPHY

A single key is used

SECRET KEY CRYPTOGHRAPHY

Sender uses the key to encrypt

Receiver uses the same key to decrypt

Key must be known to both the sender and the receiver

The difficulty is the distribution of the key

Secret key cryptography algorithms that are in use today :

SECRET KEY CRYPTOGHRAPHY

Data Encryption Standard (DES):

Advanced Encryption Standard (AES):

International Data Encryption Algorithm (IDEA):

SECRET KEY SUMMARY

Hash functions(One-way cryptography) have no key since plaintext cannot be recovered from the ciphertext.

HASH FUNCTIONS

Called message compiler and one-way encryption

HASH FUNCTIONS

No key is used

Digital fingerprint

Provide the integrity

Hash algorithms that are in common use today:

HASH FUNCTIONS

Message Digest (MD) algorithms:

HAVAL (Hash of Variable Length):

Tiger:

PUBLIC KEY CRYPTOGHRAPHY

Public Key(Asymmetric) Cryptography. Two keys are used. One for encryption, one for decryption.

PUBLIC KEY CRYPTOGHRAPHY

Developed in the last 300-400 years.

Martin Hellman and graduate student Whitfield Diffie

A two-key crypto system

Mathematical functions

Public key Cryptography

Secret key Cryptography

Secret Key Cryptography

With secret key cryptography, a single key is used for both encryption and decryption. As shown in Figure 1A, the sender uses the key (or some set of rules) to encrypt the plaintext and sends the ciphertext to the receiver. The receiver applies the same key (or ruleset) to decrypt the message and recover the plaintext. Because a single key is used for both functions, secret key cryptography is also called symmetric encryption.

Secret Key Cryptography

Public-Key Cryptography

Generic PKC employs two keys that are mathematically related although knowledge of one key does not allow someone to easily determine the other key. One key is used to encrypt the plaintext and the other key is used to decrypt the ciphertext. The important point here is that it does not matter which key is applied first, but that both keys are required for the process to work (Figure 1B). Because a pair of keys are required, this approach is also called asymmetric cryptography.

Public-Key Cryptography

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