Download - Cryptography
SOURASHTRA COLLEGE
CRYPTOGRAPHY
BY
L.S.KARNAN
II YEAR
B.Sc., Mathematics
Cryptography is the Study of art and science of keeping messages secure.
Some other authors defined the cryptography as “Cryptography
is the process of writing using various methods (“ciphers”) to keep messages secret”.
Modern Cryptography combines the studies of Computer Science and Mathematics for the purpose of Encoding information to ensure that data is secure.
CRYPTOGRAPHY:
KEYWORDS:
• Cryptography
• Cryptanalysis
• Encryption
• Decryption
• Symmetric key
• Asymmetric key
• Algorithm
HISTORY OF CRYPTOGRAPHY:
Cryptography probably began in or around
2000 B.C. in Egypt.
There are three eras in the history of Cryptography:
▪ The Manual era
▪ The Mechanical era
▪ The Modern era
Manual era:Manual era refers to pen and paper Cryptography and
dates back to 2000 B.C.
E.G. - Scytale, Caesar, Vigenere.
Mechanical era:
Mechanical era refers to the invention of cipher machines.
E.G. - Japanese Red and Purple Machines, German Enigma.
Modern era:The Modern era of cryptography refers to computers.
There are infinite permutations of cryptography available
using computers.
E.G. - Lucifer, RSA, ElGamal.
MODELS:
Ancient Cryptex Modern Cryptex
Sumerians
- Cuneiform writings Skytale
Encryption: c = Ee(p)
Decryption: p = Dd(c)
Here p is a block of plaintext,
c is a block of ciphertext,
E is the encryption function,
e is the encryption key,
D is the decryption function and
d is the decryption key.
FORMULA:
MATHSEncryption
NZGSHDecryption
MATHS
Example:
Plain text
Cipher textPlain text
NZGSH
Cipher text
{
A B C D E……………Y Z
26 25 24 23 22…………... 2 1
1 2 3 4 5……………25 26 FORWARD NUMBER
FORWARD LETTER
BACKWARD NUMBER
M - 14 - N vice - versa
A - 26 - Z
T - 07 - G
H - 19 - S
S - 08 - H
For DecryptionFor Encryption
CODING METHOD :
F.LB.N
CATEGORIES OF CRYPTOGRAPHY:
CRYPTOGRAPHERS:
Caesar Leon Battista
Alberti
Blaise de Vigenere
CRYPTANALYSERS:
APPLICATIONS:
Privacy/confidentiality
Integrity
This method is followed in Military
This method is used in ATM centers
Now-a-days, internet is very insecure therefore
Cryptography method is followed to safeguard to
transmit data.
- 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 CRYPTOGRAPHY IT'S A
LONG PROCESS.
LIMITATIONS: