Overview of Cryptographyby

Roshan Chaudhary

13ITU031

IntroductionCryptography

is the practice and

study of techniques

for secure

communication in the

presence of third

parties. Encrypted

messages can

sometimes be broken

by cryptanalysis, also

called codebreaking.

THE PURPOSE OF CRYPTOGRAPHY

Defending against external/internal

hackers

Defending against industrial espionage

Securing E-commerce

Securing bank accounts/electronic

transfers

Securing intellectual property

Avoiding liability

Some specific security requirements

Authentication

Privacy

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.

What is Encryption / Decryption

Encryption –

The process of converting plain text into

an unintelligible format (cipher text) is

called Encryption.

Decryption –

The process of converting cipher text

into a plain text is called Decryption.

What is a Key

In cryptography, a key is a variable value that is applied using an algorithm to a string or block of unencrypted text to produce encrypted text, or to decrypt encrypted text

What is a Block Cipher?

A method of encrypting / decrypting data

Key is used for encryption / decryption.

What is Initialization Vector?

An initialization vector (IV) is an arbitrary number that can be used along with a secret key for data encryption.

TYPES OF CRYPTOGRAPHIC

ALGORITHMS

Secret Key Cryptography (SKC)

Public Key Cryptography (PKC)

Hash Functions

Secret Key Cryptography

Encryption involves applying an

operation (an algorithm) to the data

to be encrypted using the private key

to make them unintelligible. The

slightest algorithm can make the

system nearly tamper proof.

Public Key Cryptography

In a public-key encryption system, users

choose a random key that only they

know. From this key, they each

automatically deduce an algorithm.

Users exchange this public key over an

insecure channel.

HASH FUNCTIONS

A cryptographic hash function is a kind

of algorithm that can be run on a piece

of data, often an individual file,

producing a value called a checksum.

Some commonly used cryptographic

hash functions include MD5 and SHA-1,

though many others also exist.

DES Encryption AES Encryption

DES uses only 56 bits key which

provides a combination of 2^56

combinations for encryption.

AES can use 128, 192, 256 bits keys

which provides 2^128, 2^192,

2^256 combinations for

encryption.

DES is restricted to use a Block Size

of only 64 bits

AES is restricted to use a Block Size

of 128 bits (double of what is used

in DES)

With 64 bits block size, the amount

of data that can be transferred

with a single encryption key is just

32GB.

With AES, it is possible to transfer

around 256 billion GB of data.

DES encryption is breakable

through Brute Force attack.

AES encryption on the other hand

is still not breakable, though there

are some theoretical discussions

about breaking the AES.

DES is an old technique used for

encryption/decryption

AES is relatively new.

Where to use cryptography ?

Anywhere you want to have something remain

secret

SSL, TLS, IPv6, SSH, IPSec all keep information secure in transit

Any Symmetric Algorithm can keep your files safe in storage

You can add encryption at the application level, or at the server level for storing database information securely

Advantages

It hides the message and your privacy is safe.

No one would be able to know what it says

unless there's a key to the code.

You can write what ever you want and how

ever you want (any theme any symbol for the

code) to keep your code a secret.

You are able to use cryptography during

lessons without the teacher knowing.

Disadvantages

Takes a long time to figure out the code.

It takes long to create the code.

If you were to send a code to another person in the past, it

will take long to get to that person.

Overall it’s a long process.

Steganography

The art and science of hiding information by

embedding messages within other,

seemingly harmless messages.

Steganography works by replacing bits of

useless or unused datain regular

computer files (such as graphics, sound,

text, HTML, or even floppy disks ) with bits of

different, invisible information

THANK YOU