Encryption

Encryption/Decryption Algorithms

Dhiraj Kumar Jha (BCT/062/405) Uday Kumar Yadav(BCT/062/424) [email protected]   http://groups.google.com/group/cryptography

What is Encryption?  Plaintext

or clear text: message sent by the communicator  Process of encoding in such a way that the outsiders can’t read is encryption  Cipher text: Encrypted message

Why Encryption?  Internet

has a threatening

danger.  Unauthorized use of unethical hackers has made secret data communication over Internet so risky.

What is Decryption? Exactly

the opposite of ENCRYPTION The sender encodes the plaintext into cipher text (ENCRYPTION) and sends to the receiver. The receiver, in turn, needs to convert into the plain text to understand the meaning of the message.

Well Known Algorithms  Caesar

(Rot 13),  Base64,  MD5,  SHA-1  RC4, RC5, DES,3DES, Blowfish, Diamond2, RSA, Rijndael Encryption Algorithm, SHA-256

Caesar (Rot 13)  Used

to encrypt plain text composed of alphabetical characters only.  Popularly known as Rot 13.  Very weak algorithm A

B

C

D

E

F

G

H

I

J

1

2

3

4

5

6

7

8

9

10

K

L

N

O

P

Q

R

S

T

11

12

M 13

14

15

16

17

18

19

20

U

V

W

X

Y

Z

21

22

23

24

25

26

Algorithm Let

us encrypt Hello Dhiraj Now first letter is H, start your count 13 letters from it i.e. U. Similarly for others. But for O, we see, we reach Z before reaching 13 count so we will continue with A again. i.e. O corresponds to B. So, our cipher text is Uryyb Quvenw Decryption is same 13 is in

Base64 One

of the most widely used and popular. Frequently used method for the Binary data/printable string conversion. Method to convert 8-bit characters to 7-bit characters, so that they can be transferred over the Internet. The Base64 system uses the following table: Code_table[0…63] = “ABCD..XYZabcd…xyz012..9+/”

Algorithm (Base64) Encoding

Step#1:

password is cryptorzz , aim how-to encode Step#2:convert into respective ASCII values, c(99),r(114),y(121)p(112)t(116),o(11 1),r(114),z(122),z(122).  Step#3 convert the decimal number into binary form  99(01100011)114(01110010)121(0 1111001)…

Contd.. Step#4

all the binary equivalents are joined or concatenated to obtain a large set of binary numbers 01100011011100100111100101 11000001110100011011110111 00100111101001111010. Step#5 now divide into equal sections only 6-bits, 12- such set obtained

Contd… Step#6

These 6-bit groups are now converted into their equivalent decimal number. 011000(24),110111(55),… Step#7 now decimal equivalents thus obtained are now changed into their Base64 values, using Base64 alphabet chart 24(y),55(3),9(J)57(5),28(c)… “cryptorzz” equivalent to “Y3J5cHRvcnp6==“ “=“ is used as padding in Base64 encryption

IP Table

Iformation Number

of IP packets received Range of size most encountered in received IP packets Average size of IP packets received Percent of total IP packets received Number of IP packets sent Range of size most encountered

Thank you all We

look forward for your comments and suggestion at the Google group  http://groups.google.com/group/cry ptography_acem