Information Security Notes 2 - Symmetric and Asymmetric Encryption
Information Security Notes 2 - Symmetric and Asymmetric Encryption
Symmetric and Asymmetric key
Symmetric
- Share Same Key
- Most classoc crypto are Symmetric
- Encrypts and Decrypts using the same key
- Also called “Secret Key Encryption”
Symmetric Overview
- More secure if the algorithm is opened and publicly review
- Two type of Symmetric
- Stream Cipher: the smallest unit to encrypt is one bit
- Block Cipher: the smallest unit to encrypt is a block
- Block Ciphers are more secure than most stream ciphers
- Most encryptions scramble the message by substitution and rearrangement for multiple-times
- Security is bounded by the key size.
- 64bits key => broken with at most 2^64 operations
History - Data Encryption Standard
DES and 3DES should not be adopted today.
- Known more by reading “Meeting in the middle attack”
Asymmetric
- Public Key
- Private Key
- Encrypt with public key; Decrypt with private key
- Also called “Public Key Encryption”
- Everyone can lock but only the one with private key can unlock
- Trapdoor Function: As a function, its function value is very easy to calculate, but the calculation of the inverse solution is very difficult unless some special information is known.