Data Security

This repository hosts:

• Securely encrypted authentication and authorization protocols written from scratch in Java. - Assignment_2
• RBAC support for the client<>server-based login system. - Assignment_2
• Token-based session management and secure password-based login.
• Secure protocols for various internet scenarios, designed by my peers and I. Written in OFMC. - Assignment_1

This repository is a repo for holding my 02239 - Data Security course materials at DTU.

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OFMC Syntax Reference

A - Variable (starts uppercase) s - Constant (starts lowercase) sk(A,B) or ck(A,B) - Shared secret key of A and B pw(A,B) - The password of A at server B pk(A) - The public key of A inv(K) - The private key that belongs to K exp(g,X) - Computes g^X via the modulo process making it too hard to undo without X {M}K - A message M encrypted by K {|M|}K - Symmetrically encrypt message M with key K {M}inv(K) - Signed message M with the private key of K h(M) - Cryptographic hash of message M (h() is a manually defined function) M1,M2,M3 - Concatenation A->B: - A is sending a message to B; note they are variables so they could be intruders

High-level Definitions

These definitions use OFMC syntax for ease of interpretation and translation.

Assymetric Encryption

In assymetric encryption (public-key encryption), every agent A has key-pair (K,inv(K)) consisting of a public key K and a private key inv(K).

Symmetric Encryption

In symmetric encryption, the same key that encrypts a message also decrypts it. Usually, two agents share a secret key K, and an agent can decrypt symmetrically encrypted message {|M|}K only if they have K.

Signatures

Signing is encrypting with private keys. {M}inv(pk(A)) is M signed by A's private key, so it can only be produced by someone who holds the full key pair (A,inv(pk(A))), aka A.

Nonces and Hashes

A nonce (number-once) is denoted by NK conventionally for K variable, and it's for ensuring duplicate messages are caught, oftentimes preventing replay attacks. It's a random number only used once.

A hash is denoted by h(M), a manually defined function.