1. Web Security

2. Simple Encryption
In cryptography, encryption is the process of encoding messages or information in such a way that only authorized parties can read it

3. Substitution Cipher Example
Ciphertext: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD Plaintext: the quick brown fox jumps over the lazy dog

4. Classes of Cryptographic Algorithms
Symmetric Algorithms – Uses the same cryptographic key for both encryption and decryption (i.e., shared secret)
Asymmetric Algorithms – Requires two separate keys, one is secret (private) and one is public; the keys are mathematically linked

5. The key and algorithm must be shared between Bob and Alice
Symmetric Encryption
Man In The Middle
Bob
Alice
Algorithm
Cipher Text
Plain Text
Plain Text
Cipher Text
Key
The key and algorithm must be shared between Bob and Alice

6. Asymmetric Encryption
Also known and public-key cryptography
Each person has a pair of keys (public and private)
Any person can encrypt a message for a specific person
Based on cryptographic algorithms that use mathematical problems that currently have no efficient solution
Public-key algorithms are the fundamental security ingredients for almost all Internet security
Underpins Internet standards such as Transport Layer Security (TLS), S/MIME and PGP
Can also be used for digital signatures, in which a message is signed with the sender’s private key and can be verified by anyone who has access to the sender’s public key

7. Key Generation

9. Certificate Authorities
An entity that issues digital certificates
A digital certificate certifies the ownership of a public key by the named subject of the certificate
A client uses a CA certificate to verify the CA signature on a server certificate

10. What’s Needed For Secure Communication Between Client and Web Server?
1) Client needs to prove the web server is who it says it is 2) Client needs to share information with web server in a secure fashion #1 Is solved with certificates #2 is solved with asymmetric and symmetric encryption of messages

11. How Communication Works

12. YouTube Explanation