A Concise Introduction to Cryptographic Concepts by Gokul Alex in the ALTERED 2020 Virtual Conference Organised by IEEE Kerala Section in MBCET. This session covers the historic emergence of cryptographic schemes such as Ceaser Cipher, Substitution Cipher, Transposition Cipher, Vigenre Cipher, Vernam Cipher, One Time Pad, RSA, Diffie Hellman, Elliptic Curves, Hash Algorithms etc.

1. APPLIED CRYPTOGRAPHY
Fundamental Facets and Future Frontiers

3. APPLICATIONS
Disk Encryption
Digital Certificates
Digital Signatures
HTTPS
HTTP/2
HTTP/3
Wifi
GSM

4. BASIC TERMS
Encryption
Decryption
Plain Text
Cipher Text
Cipher
Key

6. TYPES OF CRYPTOGRAPHY
Symmetric Cryptography
Synonyms : Private Key, Secret Key, Shared Key, One Key
Asymmetric Cryptography
Synonyms: Public Key

7. SYMMETRIC CRYPTOGRAPHY
Block Ciphers
Stream Ciphers
Cryptographic Hash Functions
Message Authentication Codes

8. A CIPHER IS A DIGITAL LOCK

9. CAESAR CIPHER WAS USED IN
WARS AROUND 50 BC

11. BLOCK CIPHER
A block cipher is an encryption method
that applies a deterministic algorithm
along with a symmetric key to encrypt
a block of text.

12. STREAM CIPHER
A stream cipher is a symmetric key cipher
where plaintext digits are combined with a
pseudorandom cipher digit stream. In a
stream cipher, each plaintext digit is
encrypted one at a time with the
corresponding digit of the keystream, to give
a digit of the ciphertext stream.

14. VIGENERE CIPHER
The Vigenère cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar
ciphers, based on the letters of a keyword. It employs a form of poly-alphabetic substitution.

16. VIGENERE CIPHER IMPLEMENTATION
• Encryption
• The plaintext(P) and key(K) are added modulo 26.
• Ei = (Pi + Ki) mod 26
• Decryption
• Di = (Ei - Ki + 26) mod 26

17. BASICS OF MODULAR ARITHMETIC

18. HASH ALGORITHMS
< Code >
importhashlib
print(hashlib.algorithms_guaranteed)
< Output >
{'md5', 'sha256', 'blake2b', 'sha1',
'sha3_512', 'sha3_224', 'shake_256',
'sha3_256', 'shake_128', 'sha512',
'sha224', 'sha384', 'blake2s', 'sha3_384'}

19. HASHING A STRING
importhashlib
str=“Altered2020”
result =hashlib.sha256(str.encode())
print(result.hexdigest())
result =hashlib.sha384(str.encode())
print(result.hexdigest())
result =hashlib.sha224(str.encode())
print(result.hexdigest())
result =hashlib.sha512(str.encode())
print(result.hexdigest())
result =hashlib.sha1(str.encode())
print(result.hexdigest())

20. MULTI LAYER ENCRYPTION
Also known as multiple encryption, cascade
encryption and cascade ciphering
It has multiple levels
First layer of encryption is to use generating cipher
text, hashing algorithms and symmetric keys
Second layer of encryption is the process of adding
more layers to cipher text with same or different
algorithms.
Third layer of encryption is about transmitting the
encrypted capsule through encrypted channels
such as SSL / TLS

21. HYBRID CRYPTOGRAPHY
Hybrid cryptography is the process of using multiple ciphers of
different types together by including benefits of each of the cipher.
There is one common approach which is usually followed to generate
a random secret key for a symmetric cipher and then encrypt this key
via asymmetric key cryptography.

22. VERNAM ONE TIME PAD
Modulo Arithmetic Based Addition Of A
Clear Text With a Key, A Random Chosen
and Of the Same Size Or More than That
of the Clear Text
The operation is fully bijective and can be
undone, just like a classical math addition
Same Key is used for encryption and
decryption. Hence it is called as
symmetric encryption system

23. RSA
ENCRYPTION
( 1977 )
Ron Rivest
Adil Shamir
Leonard Adelman

28. DFH KEY
EXCHANGE
ALGORITHM
( 1976 )
Whitfield Diffie
Martin Hellman

29. DIFFIE HELLMAN APPROACH
The Diffie-Hellman approach has each party generate both a public and private key, but only the
public key is shared. Once the client on either end of the transaction has verified the other person’s
public key, the exchange can be shared.

34. ELGAMAL
CRYPTOSYSTEM
Tahar Elgamal (1985)

43. ELLIPTIC CURVE
CRYPTOGRAPHY
( 1985 )
Victor Miller
Neal Koblitz

44. ELLIPTIC
CURVES
It is based on the algebraic structure
of elliptic curves over finite fields.
It has horizontal symmetry
Any non-vertical line will intersect
the curve in three places at the most