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1. Secret Key
Cryptography

2. Contents
Introduction
What is Secret Key
Cryptography ?
Examples of Secret
Key Cryptography.
Uses of Secret Key
Cryptography.
Difference
Between Private
Key and Public Key.
Secret Key
Cryptographic
Algorithms.
Advanced
Encryption
Standard (AES)
Triple Data
Encryption
Standard (3DES)
Rivest Cipher 4
(RC4)
Advantages of
Secret Key
Cryptography.
Disadvantages of
Secret Key
Cryptography.

3. Introduction
Secret key cryptography is effective for communication over insecure
channels as the piece of information or parameter used helps the information
to encrypt and decrypt messages.
There are two different keys used for asymmetric encryption in which one is a
public key, the other is a secret key.
A secret key may also be known as a private key.

4. What is Secret Key Cryptography ?
THE SECRET KEY CRYPTOGRAPHY IS USED TO ENCRYPT
THE PLAINTEXT MESSAGE USING A SERIES OF BITS
CALLED THE SECRET KEY.
IT OFTEN USES THE SAME KEY TO DECIPHER THE
CORRESPONDING CIPHERTEXT MESSAGE AND TO
RETRIEVE THE INITIAL PLAIN TEXT BECAUSE BOTH
ENCRYPTING AND DECRYPTING DATA IS ACHIEVED
WITH THE SAME KEY, A SECRET KEY IS OFTEN CALLED
AS A SYMMETRIC KEY.
THE SECRET KEY IN CRYPTOGRAPHY IS ALSO AN INPUT
FOR ENCRYPTION ALGORITHM AS THIS IS THE INITIAL
INTELLIGIBLE MESSAGE OR DATA THAT IS FED INTO
THE ALGORITHM AS INPUT.

5. What is Secret Key Cryptography ? ( cntd.)
The main is an algorithm value
independent from the plaintext.
Depending on the particular key
used the algorithm outputs a
different result. The algorithm
relies on the key to exact
substitution and transformation.
This is the scrambled message that
has been generated as production.
It depends on the plain text and on
the secret key.
Two different keys can generate
two different ciphertexts for a given
letter.

6. What is Secret Key Cryptography ? ( cntd.)
The ciphertext is an almost random stream of data which as it stands.
Decryption algorithm is basically a reverse-run encryption algorithm.
It takes the ciphertext and the secret key, and it generates the original plain text. In this type of
cryptography, both the sender and the receiver must know the key, that it is in effect, the
password.
The main distribution, of course, is the greatest challenge with this method.

7. Example of Secret Key Cryptography
A very basic method for encrypting messages is to replace each letter of the message
with one that is several more places in the alphabet. The secret is the number of places.
For eg, the message “This is an example” can be encrypted using the key “1
position” in the encrypted message “Uijt jt bo fybnqmf”
Taking a letter that is 1 position above in the alphabet would end in the original
message again.
This device is not very stable. Just twenty-six keys are possible.

8. Example of Secret Key Cryptography ( cntd.)
One should only try all the keys and
see which one can result in a
readable message.
In addition, it is well known that
certain letters appear more often in
communications than others.
For example, the letter “e” is the
most used letter in the English
language.
Using this reality, simply count the
letter appears most frequently in
the encrypted message and
substitute it with the letter “e”.
Then we knows how many places
we needs to rotate to get from “e”
to the encrypted version of “e”.

9. Uses of Secret Key Cryptography
With secret key encryption, both
Alice and Bob communicators use
the same key to encrypt and
decode texts.
Before any encrypted data may
be transmitted across the
network, both Alice and Bob must
have the key and agree on the
cryptographic protocol to be used
for encryption and decryption.
One of the big issues with secret
key cryptography is the logistical
dilemma of how to get the key
from one party to the other
without giving access to the
attacker.
If Alice and Bob protect their data
with secret-key cryptography, and
if Charlie has access to their key,
Charlie will understand any secret
messages that Alice and Bob
intercept.

10. Use of Secret Key Cryptography ( cntd.)
Not only can Charlie decode
the messages of Alice and
Bob, but he can also believe
that he is Alice and send
encrypted data to Bob.
Bob is not going to realize
that the letter came from
Charlie, not Alice.
When the issue of secret key
dissemination is overcome,
secret key cryptography may
be a powerful method.
Algorithms provide excellent
protection and encrypt data
reasonably easily.

11. Use of Secret
Key
Cryptography (
cntd.)
• The bulk of confidential data transmitted during an SSL session is sent using
secret-key cryptography.
• Secret key cryptography is often called symmetric cryptography since the
same key is used to encrypt and decrypt data.
• Well-known hidden key cryptographic algorithms include Data Encryption
Standard (DES), triple-strong DES (3DES), Rivest Cipher 2 (RC2), and Rivest
Cipher 4 (RC4).

12. Difference between Private Key and Public Key
Public Key Private Key
Theirs is no possibility of loss since one
the requirement is a public key
Once Lost , the file will become unusable
One Key is publicly available The Key is kept secret by two people
It is commonly used to secure web
sessions
It is commonly used to protect disk
drives and other data storage devices.
It is a form of asymmetrical encryption. It is a form of symmetrical encryption.
It is slower since two keys are required It is faster since only one key is needed

13. Secret Key
Algorithms
ADVANCED ENCRYPTION
STANDARD (AES)
TRIPLE DATA ENCRYPTION
STANDARD (3DES)
RIVEST CIPHER 4 (RC4)

14. Advanced Encryption Standard (AES)
The AES Encryption algorithm (also known as the
Rijndael algorithm) is a symmetric block cipher
algorithm with a block/chunk size of 128 bits.
It converts these individual blocks using keys of
128, 192, and 256 bits.
Once it encrypts these blocks, it joins them
together to form the ciphertext

15. Triple Data Encryption Standard (3DES)
3DES Encryption, also known as
Triple Data Encryption Standard
(DES), is a type of cryptography
where block cipher algorithms
are applied three times to each
data block.
The key size is increased in
Triple-DES to ensure additional
security through encryption
capabilities.
Each block contains 64 bits of
data

16. Rivest Cipher
4 (RC4)
RC4 STANDS FOR RIVEST CIPHER 4. RC4 IS A STREAM CIPHER AND WAS
INVENTED BY RON RIVEST IN 1987.
SINCE RC4 IS A STREAM CIPHER, IT
ENCRYPTS THE STREAM OF DATA BYTE BY
BYTE.
OF ALL THE STREAM CIPHERS, RC4 IS THE
WIDELY USED STREAM CIPHER DUE TO ITS
SPEED OF OPERATIONS AND SIMPLICITY.

17. Advantages of
Secret Key
Cryptography
High rates of data throughput, with
hardware solutions up to hundreds
of megabytes per second .
Key length is relatively short.
Symmetric – Key ciphers can also
be combined to produce stronger
ciphers.

18. Disadvantages
of Secret Key
Cryptography
The Key must remain secret
at both ends.
Cryptographic practice leads
to frequent key change.
In large networks, many key
pairs have to be managed.