cryptography notes

1. DES/3DES
2. AES
3. RC4, RC5 and RC6
4. twofish
   • Symmetric key block cipher
   • block size: 128 bits
   • Key size: up to 256 bits
   • Key-dependent S-Boxes: obscure relationship of key and cipher
5. DSA (Digital Signature Algorithm)
   • 2 phases of key generation:
   • choice of algorithm paramaters (shared between different users)
   • computes public and private keys for users
   • ECDSA (Elliptic Curve Signature Algorithm) (Remember the Sony PS3 hack)
6. RSA (Rivest Shamir Adleman)
   • Asymmetric
   • Each user has his/her own private key. Public keys are shared.
7. Diffie-Hellman (DH)
   • …a way of generating a shared secret between two people in such a way that the secret can’t be seen by observing the communication…
   • Alice and Bob more info
8. MD5, SHA, RIPEMD-160, HMAC
   • MD5 (Message Digest Function)
     • 128-bit value
     • non-identical messages can have the same hash value (collision!!)
   • SHA (Secure Hashing Algorithm)
     • SHA-1: 160-bit hash value
     • SHA-2: 224, 256, 384 and 512 bit
     • SHA-3: 512 bit value, sponge construction
   • RIPEMD-160 (RACE Integrity Primitives Evaluation Message Digest)
     • 160-bit
   • HMAC (Hash-based Message Authentication Code)
     • cryptographic hash function and cryptogrpahic key
     • integrity and authentication
     • can be used with other algorithms: HMAC_MD5("key","the quick brown fox jumps over the lazy dog")

Related Tools:

• HashCalc
• online md5 decryption tool

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1. PKI (Public Key Infrastructure)
   • roles, policies and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public key encryption
   • bind public keys to entities
   • CA (Certificate Authority)
   • RA (Regisration Authority)
   • Web of trust (self-signed)

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Email Encryption

• DSA (Digital Signature Algorithm)
• SSL (Secure Sockets Layer): See “Poodle” Vulnerability
• TLS (Transport Layer Security)
  • TLS 1.2
    • SHA-256
    • Removed SSL capability
  • TLS 1.3
  • Removed support for MD5, SHA-224, weak elliptic curves
  • Every bytes explained and reproduced
• PGP (Pretty Good Privacy)
  • End-to-end encryption
  • OpenPGP Standard (RFC 4880)
  • Hashing, Data Compression, Symmetric, Assymetric

Related Tools:

• OpenSSL
• keyczar
• GnuPG

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Attacks

1. Brute-Force: passwords/passphrases
2. Birthday
3. Meet-in-the-Middle: space-time tradeoff
4. DUHK (Don’t Use Hard-coded Keys)
5. Rainbow Table