Overview of Cryprography: Private,Public key and Hash Functions.

1. Overview of Cryptography
by
Roshan Chaudhary
13ITU031

2. Introduction
Cryptography
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.

3. 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

4. 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.

5. 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.

6.  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.

7. TYPES OF CRYPTOGRAPHIC
ALGORITHMS
Secret Key Cryptography (SKC)
Public Key Cryptography (PKC)
Hash Functions

8. 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.

9. 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.

10. 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.

12. 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.

13. 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

14. 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.

15. 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.

16. 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

17. THANK YOU