Data Encryption

Data Encryption

INTRODUCTION Cryptography is the science of secret

using mathematics to encrypt and decrypt data.

Scrambling a message so that it’s contents are not readily accessible.

Decryption is the reverse of encryption.

Enables storage of sensitive information (from one’s personal diary to secrets of a nation).

Depends upon particular algorithms known as ciphers.

A process to convert plaintext (unencrypted text) into cipher text (encrypted text).

Keys are the soul of modern encryption.

Encryption Yesterday MASKING or Substitution is…

Individual characters being shifted by n numbers down or up the alphabetic table.

HELLOSIR becomes NKRRUYOX (A -> G)

VEILING or Transposition is..

Covering up of plaintext by first changing them into blocks of n characters each and exchanging the position of characters in each block.

(1234->3142) 1234 Plain text:DATA ENCR YPTI ONRE PORT

3142 Cipher: TDAA CERN TYIP ROEN RPTO

Simple Mathematics based algorithm and easier to decrypt.

Encryption Today Based on a specific ‘key’ or

‘password’ and the encryption algorithm alters itself such that different keys will produce different cipher texts.

The algorithm can be either

symmetrical (single key) or

asymmetrical (two keys – one for encryption and one for decryption).

Symmetric Encryption

Decryption Process

Fig: Simple process of symmetric encryption

Encryption Process

Symmetric Encryption

Are of two types.Stream Cipher (text encrypted and decrypted a letter at a time)Block Cipher (blocks of text encrypted or decrypted at a time)

Following common types of algorithm.Data Encryption Standard (DES)International Data Encryption Algorithm IDEA)RC2 and RC4Advance Encryption Standard (AES)

DES encryption has already been broken.

Algorithms like AES, IDEA, RC2 and RC4 and also 3-DES are very strong encryption system and to crack them takes a lot of time.

Unencrypted

Encrypted

by IDEA

Encrypted

by 3DES

Disadvantage of Symmetric Encryption Keys can be transmitted only through secure channels.

Data is not certified, so the authenticity of received cipher text is not verified.

If there are n number of users connected in a network, number of keys to facilitate 1 to 1 communication between each user becomes

nC2=n(n-1)/2

Third Party Accessing The

Information

Asymmetric Encryption

Fig: Simple process of asymmetric encryption

Global User accessing Public Key

Server Containing Encrypted Text

Message Transmitted

Using A’s Public Key A

A Uses his

Private Key to decrypt cipher text

Rivest, Shamir, Adleman (RSA) Use of two keys suppose K1 and

K2. Encryption by K1 and Decryption

by K2 or vice versa. Impossible to derive K1 from K2

or vice versa. Basis of RSA algorithm is that it

is easy to multiply two large prime numbers, but very difficult to find its prime factors.

A public key Algorithm.

DIAGRAM

Plain Readable Text

Plain Readable Text

10101010101011010101010101

Plain Readable Text

Plain Readable Text

Private Key

Public Key

Disadvantage of Asymmetric System

Disadvantage of Asymmetric Key Encryption

Is about 1000 times slower than symmetric encryption.

Encrypted text is about double that of plaint text.

Symmetric Asymmetric

Speed

Modern techniques of encryption Modern technique Hybrid encryption system Plain text is encrypted using

Symmetric encryption The generated key is then

encrypted using receiver’s public key.

ExamplesPGP – Pretty Good Privacy

SSL – Secure Socket Layer

Modern techniques of encryption

Plain Readable Text

Plain Readable Text

Plaintext is encrypted with session key Session Key is

encrypted with public key

Encrypted Session Key +

Cipher Text

Data Authenticity

User A wants to Send message to

B

Z intercepting Data

from A and

Sending it to B

B receives message

AB

Z

Hash function and Digital signature

Hash Function

Digital Signature

with private Key

Message Digest

Private Key

Plaintext

+

Signature

Working of Hash Function and Digital Signature

About Digital Signature Implemented through public-key

encryption Used to verify the origin and contents of

a message. Uses the private key of the sender to

verify his/her authenticity.

About Digital Certificate

Digitally signed and issued by Certificate Authority.

Verifies that the public key attached to the certificate belongs to the party stated.

Example of Digital Certificate

Yahoo Messenger “ymsg.exe” digitally signed by Yahoo Inc.

Applications and Services Military secrets Telecommunication E-commerce and E-business Internet banking Internet voting Music piracy

Military Secrets

MILITARY communication.

MILITARY Arms and ammunition information.

MILITARY database.

E-commerce and E-business

► Secure internet communication and

exchange of information.

► Electronic transactions

► Use of credit cards and debit cards.

► Privacy in internet content like emails.

► Digital authenticity of data.

► Non-repudiation ensures honesty.

Time Based Cryptography► Encryption for specific period of

time

► Decryption cannot be done until

particular interval of time or

specific date

Applications► Tender filling

► Will and Property Secrets

► Time encrypted checks

101010101001100001101010

Thank you

Questions?

Bibek ShresthaLakesh KansakarManish Modi

BCT - 061Institute of EngineeringPulchowk

Basic Process – Asymmetric Encryption

Two large prime numbers A and BC = A * BOther 2 prime numbers D and E chosen such that (D * E) mod (A-1)(B-1) = 1

Public Keys are (E,C)Private Keys are (D,C)

To encrypt X(X ^ E) mod C = encrypted text YTo decrypt Y(Y ^ D) mod C = decrypted text X

Simplified Example of asymmetric keyA = 47 and B = 71C = A * B = 3337(A – 1)(B – 1) = 46 * 70 = 3220D = 79 and E = 1019(79 * 1019) mod 3220 = 1

Encrypt password (79, 3337)Decrypt password (1019, 3337)

To encrypt 2001(2001 ^ 79) mod 3337 = 2563

To decrypt 2563(2563 ^ 1019) mod 3337 = 2001

Original Keys Given by RSAC= 114,381,625,757,888,867,669,235,779,976,146,612,010,218,296,721,242,362,562,561,84

2,935,706,935,245,733,897,830,597,123,563,958,705,058,989,075,147,599,290,026,879,543,541

encryption key (E)= 9007(E, C)