encryption methods and explanation

2. Clear text or plain text
Messages that are readable and
understandable by any individual is
referred to as clear text or plain text.
Ex: “HELLO”

3. Encryption
Transformation of data into a form that is
unreadable by anyone who does not
possess the secret key.
Ex: HELLO
Cipher text 5%$$K

4. Decryption
Cipher text is unreadable, so to read and
understand the message the encrypted or cipher
text is transformed back to clear text.
“The process of restoring the cipher text to
plain text is called decryption.”
Ex: 5%$$K
HELLO

5. Encryption cryptographic mechanisms
Symmetric
cryptography
Entities share a
common secret
key.
Asymmetric
cryptography
Entities share a public
key cryptography
where each
communicating entity
has a unique key pair.

6. Symmetric Encryption Keys

7. Data Encryption Standard (DES)
• DES is a primary symmetric encryption algorithm.
• DES is a block cipher based encryption technique
based on a 56-bit key.
64-bits fixed
block of clear
text
transforms
64-bits fixed
block of
cipher text

8. 1. Scramble 64-bit text block for one time
H E L L O !
2. Divide 64-bit block into two 32-bit blocks
3. scramble 16 times using secret DES key.
E L H O ! L
4. Apply inverse of the initial scramble.
L H E ! L O

9. Asymmetric Encryption Keys
Sender
Determines secret – a
Public A made available
Retrieve public B &
compute key from secret –
a & public B
Receiver
Determines secret – b
Public B made available
Retrieve public A &
compute key from secret –
b & public A
Clear text
message encrypt decryptEncoded message
Clear text
message
Identical keys generated
(a, B) (b, A)