Security

Encryption

Symmetric

Alice and Bob have two identical Keys that can encrypt and decrypt messages (Alice encrypts, sends + Bob receives, decrypts)

pros:

• easy to use, fast cons:
• we can’t safely exchange keys with this method

Asymmetric

Alice and Bob each have their own pair of Keys(Lock and Key OR Private and Public) (Alice sends lock + Bob receives lock, decrypts, sends + Alice decrypts)

based on RSA algorithm

slow, but good for initial connection

one problem: middle man(where hacker can receive and change data in between messaging)

Certificate Authority

authority is signing public key of Alice, which includes meta-data that confirms that Alice is Alice + Bob checks if Alice is Alice and after that init connection

fixes middle man problem

Web Security

Password Sending

• password field hides content
  • can be set by type
• form is sending requests in POST method

Auth

• login+pass can be set as cookie, so every request from client will contain this info
  • it is not safe, so we can instead generate some session token with lifetime and set it as cookie instead
    • session token is key for value(info about user)
    • session token can also be without auth, so server can track user cations before auth

Password

• brute force
  • we can send one joined error for password and username, so it is harder to find if user exists
  • number of login tries must be limmited
• safety
  • password must be hashed(transformed to some string that can’t be used to calculate password back, but be identical for same inputs)
    • this prevents password leak if data base is stolen
  • password must be salted before hashing, so same passwords won’t output same hashes
    • prevents possibility to just compare our hash with predefined list of hashes
    • salt is stored as part of user data and uniq for each user

CSRF Attack

CSRF - cross-site request forgery

some other site can sent request to our back-end with cookies inside our browser and appear as legit user

to prevent this we can use csrf token

• it is done by adding additional hidden field with csrf token as value
• this token is stored as part of session data

XSS Attack

XSS - cross-site scripting

happens if some external script was added to generated webpage

• parsed from template
• injected from user input

can be in form of direct script tag or as attribute

to prevent:

• validate, escape and sanitize data
• use frameworks that disallow direct HTML input like React

SQL injection

happens when arguments to SQL command aren’t sanitized and added to SQL request directly

to prevent:

• validate, escape and sanitize data
• ORM and other frameworks has built-in solutions