Cryptography in Human computer interaction powerpoint

A presentation on the unit of Cryptography found in the Human Computer Interaction course.

1. Cryptography

2. Cryptographic Variations
•Key: Public vs Private
•Ciphers: Stream vs Block
•Techniques: Substitution vs Permutation
•Ciphers:
Ceaser(https://www.youtube.com/watch?v=JtbKh_12ctg) vs
Playfair
(https://www.youtube.com/watch?v=JtbKh_12ctg&list=TLPQMTUw
MjIwMjTsYs2g699cLg&index=1),
https://www.youtube.com/watch?v=hHsUJxikM3gvs
Vegenere(https://www.youtube.com/watch?v=Ic4BzVggNY8) vs
Hill(https://www.youtube.com/watch?v=-EQ8UomTrAQ)
Steganography: https://www.youtube.com/watch?v=Te8Cao2Smsk
•Algorithms: RSA vs DSA
•Protocols: SSH vs SSL vs TLS
•Standards: DES vs AES

3. Cryptography
•Cryptography is the practice and study of hiding
information
•It is the art or science of converting a plain data into a
format that cannot be understood (cipher) by attackers
•Prevent brute-force, MITM, cryptanalysis, phishing, side-
channel, and birthday attacks
•Cryptography is aimed at providing confidentiality, integrity
and accuracyof transmissions
•Encryptionis the process of converting plain data to cipher
and decryptionis the process of converting cipher to plain
data

4. Symmetric Key Cryptography
•Also called Secret Key Cryptography uses the samekey for
both the sender and receiver
•The keys must be kept secret and securely distributed, thus,
also called “Secret Key Cryptography”
•It is simpleand faster but less secure, but used when data is
large

5. Asymmetric Key Cryptography
•Also called public key cryptography uses two
different keys so that users get the key from a
Certificate Authority
•It is more secureand authenticbut relatively
complex and slow for small data

6. Stream Vs Block Cipher
•Stream Ciphers and block ciphers are two
categories of ciphers used in classical
cryptography.
•Stream and Block Ciphers differ in how largea
piece of the message is processed in each
encryption operation.
•Stream ciphers encrypt plaintext one byte or
one bit at a time.
•Block ciphers encryptplaintextin chunks.
Common block sizes are 64 and 128 bits

7. Block Cipher
•Divide input bit stream into n-bit sections, encrypt only that section, no
dependency/history between sections
•In a good block cipher, each output bit is a function of all n input bits and all k key
bits

8. Stream Vs Block Ciphers

9. Confusion and Diffusion
•Terms courtesy of Claude Shannon, father of Information
Theory
•“Confusion” = Substitution
•a -> b
•Caesar cipher
•“Diffusion” = Transpositionor Permutation
•abcd -> dacb
•DES
Encryption Decryption
plaintext ciphertext plaintext
Key K
A Key K
B

10. Examples of Ciphers
•Simple and non-secure ciphers
–Shift Cipher –Caesar Cipher
–Affine Cipher
–Vigenere Cipher
–Hill Cipher
•Information-secure cipher
–One-Time Pad

11. Caesar Cipher
•https://www.youtube.com/watch?v=JtbKh_12
ctg; Caesar Cipher
•https://www.youtube.com/watch?v=na5rapg1
XsI; Brute-force attack on Ceaser Cipher
(Cryptanalysis attack)
•https://www.youtube.com/watch?v=DoBqnt7
Bf24Brute-force attack

12. Confusion
•Modern substitution ciphers take in N bits and
substitute N bits using lookup table: called S-Boxes
•“Confusion” : a classical Substitution Cipher
•Caesar cipher
Encrypt(Letter, Key) = (Letter + Key) (mod 26)
Decrypt(Letter, Key) = (Letter -Key) (mod 26)
Encrypt(“NIKITA”, 3) = “QLNLWD”
Decrypt(“QLNLWD”, 3) = “NIKITA”

13. Playfair Cipher
•https://www.youtube.com/watch?v=UURjVI5c
w4g; Part 1
•https://www.youtube.com/watch?v=whEJfas9
MAI; Part 2
•https://www.youtube.com/watch?v=hHsUJxik
M3g&t=487s; Question solved

14. Hill Cipher
•https://www.youtube.com/watch?v=-
EQ8UomTrAQ; Encryption
•https://www.youtube.com/watch?v=JK3ur6W
4rvw; Decryption

15. Transposition
•https://www.youtube.com/watch?v=knE4G8D
GLoY; Rail Fence Technique
•https://www.youtube.com/watch?v=cPQXaYU
MOjQ; Row Column Transposition

16. Diffusion
•“Diffusion” : a classical Transposition cipher
•modern Transposition ciphers take in N bits and
permute using lookup table : called P-Boxes

17. Steganography
•https://www.youtube.com/watch?v=Te8Cao2
Smsk; steganography
•https://www.youtube.com/watch?v=yNo58UiI
MKU; LSB Steganography

18. •DSA stands for Digital Signature Algorithm.
•It is a cryptographic algorithm used to generate digital
signatures, authenticate the sender of a digital message,
and prevent message tampering.
•DSA works by having two keys: a private key owned by
the sender and a public key held by the receiver.
–The sender uses their private key to generate a signature for
the message, which is then sent along with it.
–Then, the message receiver uses the sender's public key to
verify that the signature is valid and that the message has not
been tampered with.
–The verification process is done using unique algorithms that
allow the receiver to validate the signature without having
access to the sender's private key
Digital Signature Algorithm

19. The image above shows the entire procedure of the DSA algorithm. You will use two
different functions here, a signing function and a verification function.
The difference between the image of a typical digital signature verification process
and the one above is the encryption and decryption part.
(https://www.simplilearn.com/tutorials/cryptography-tutorial/digital-signature-
algorithm#:~:text=DSA%20stands%20for%20Digital%20Signature,key%20held%20b
y%20the%20receiver. )
Digital Signature Algorithm

20. RSA Algorithm
The RSA algorithm is a public-key signature algorithm developed by Ron Rivest, Adi
Shamir, and Leonard Adleman (RSA) to implement digital signature authentication
An algorithm that uses logarithmic functions to keep the working complex enough to
withstand brute force and streamlined enough to be fast post-deployment.
The image below shows it verifies the digital signatures using RSA methodology
RSA can also encrypt and decrypt general information to securely exchange data
along with handling digital signature verification
(https://www.simplilearn.com/tutorials/cryptography-tutorial/rsa-algorithm).

21. RSA DSA
It is a cryptosystem algorithm. It is digital signature algorithm.
It is used for secure data transmission.
It is used for digital signature and its
verification.
It was developed in 1977. While it was developed in 1991.
It was developed byRon Rivest,Adi
ShamirandLeonard Adleman.
It was developed byNational Institute of
Standards and Technology (NIST).
It uses mathematical concept of
factorization of product of two large
primes.
It uses modular exponentiation and
discrete logarithm.
It is slower in key generation.
While it is faster in key generation as
compared to RSA.
It is faster than DSA in encryption.While it is slower in encryption.
It is slower in decryption. While it is faster in decryption.
It is best suited for verification and
encryption.
It is best suited for signing in and
decryption.

22. Secure SHell
•Or SSH is anetwork protocolthat gives users, particularly system
administrators, a secure way to access a computer over an
unsecured network
•Provides a strong passwordauthenticationandpublic
keyauthentication, as well asencrypteddata communications
between two computers connecting over an open network, such as
the internet
•used by network administrators to manage systems and applications
remotely, enabling them to log in to another computer over a
network, execute commands and move files from one computer to
another
•SSH can also be used to create secure tunnels for other application
protocols, for example, to securely run X Window System graphical
sessions remotely. An SSH server, by default, listens on the standard
Transmission Control Protocol (TCP) port 22

23. SSH vs Telnet
•Telnetwas one of the first internet application protocols --
the other is FTP. It is used to initiateand maintaina
terminal emulation session on a remote host.
•SSH and Telnet are functionally similar, with the primary
difference being that the SSH protocol usespublic key
cryptographyto authenticate endpoints when setting up a
terminal session, as well as for encryptingsession
commands and output.
•While Telnet is primarily used for terminal emulation, SSH
can be used to do terminal emulation --similar to
therlogincommand --as well as for issuing commands
remotely as with rsh, transferring files using SSH File
Transfer Protocol (SFTP) and tunneling other applications

24. SSH vs. SSL/TLS
•The Transport Layer Security (TLS) protocol, which updates the Secure Sockets
Layer (SSL) protocol, was designed to provide security for network transmissions
at the transport layer. The SSH protocol also operates at or just above the
transport layer, but there are important differences between the two protocols.
•While both rely on public/private key pairs to authenticate hosts, only the server
is authenticated with a key pair under TLS. SSH uses a separate key pair to
authenticate each connection: one key pair for a connection from a local
machine to a remote machine and a second key pair to authenticate the
connection from the remote machine to the local machine.
•Another difference between SSH and TLS is that TLS enables connections to be
encrypted without authentication or authenticated without encryption. SSH
encrypts and authenticates all connections.
•SSH provides IT and information security (infosec) professionals with a secure
mechanism to manage SSH clients remotely. Rather thanrequiring password
authenticationto initialize a connection between an SSH client and server, SSH
authenticates the devices themselves. This enables IT staff to connect with
remote systems and modify SSH configurations, including adding or removing
host key pairs in the known hosts file

26. Data Encryption Standard (DES)
•DES is a previously predominant algorithm used for
encryption/decryption of electronic data
•Like other private key cryptographic methods, both the
sender and the receiver must know and use the same private
key
•DES uses a 56 bit encryption key which can be around 2
56
()
combinations to encrypt the plain text. DES is restricted with
a Block Size of just 64 bits
•Sometimes DES is said to use 64 bit key, but 8 bits out of it is
used for some other purposes
•The maximum amount that can be transferred with a single
encryption is 32GB. DES uses FeistelNetwork (Transposition,
permutation, “diffusion”) which divides block into 2 halves
before going through the encryption steps e.gabcd->dacb

27. Advanced Encryption Standard (AES)
•AES is a specification for the encryption of
electronic data
•The algorithm described by AES is a Symmetric-Key
Algorithm, meaning the same key is used for
encrypting and decrypting data
•The block size is restricted to 128 bits and the key
size of 128, 192, 256 bits can be used
•AES is based on a design principle known as
substitution (confusion) network e.g a -> b, and is
fast in both software and hardware