Hash

Note: above diagram comes from cheapsslsecurity

It has following properties:

• Generally, hash is smaller than its original data
• Hash value is fixed length for one type hash algorithm
• Same data will always produce same Hash
• Impossible to revert hash value back to original data
• No collision, different text corresponds to different hash
• Unpredictability, if we change even a single character in the input (actually even a single bit), on average 50% of the output bits will change

Common Usage

1. check content integrity
2. store user password

Encryption

Symmetric

It uses same key to encrypt and decrypt.

Asymmetric

It uses public key to encrypt and private key to decrypt.

The public key, as its name implies, is public which means it can be passed over the internet.

Hybrid

Combine symmetric with asymmetric.

Hash vs Encryption

	Hash	Symmetric	Asymmetric
no. of keys	0	1	2
recommended length	256 bits	128 bits	2048 bits
commonly used algorithm	SHA	AES	RSA
key distirbution	N/A	big issue pass the key over internet	easy & secure
speed	fast	fast	relatively slow
complexity	medium	medium	high

Encoding

Encoding is not used for security purpose.

Fundamentally, it is just a technique to transform data into other formats so that it can be consumed by others.

The same algorithm, such as ASCII, is used to encode and decode.

Reference

difference-between-hashing-and-encryption

symmetric-vs-asymmetric

encryption-symmetric-asymmetric-hashing