Encryption Algorithms Reference

A quick reference for encryption algorithms, their types, key sizes, and use cases. Know these for the CISA exam's information asset protection domain.

Symmetric Encryption (Shared Key)

Both sender and receiver use the same key. Fast for bulk data encryption. Key distribution is the main challenge.

Algorithm	Key Size	Type	Status
DES	56 bits	Block cipher	Deprecated (insecure)
3DES	112 or 168 bits	Block cipher	Legacy (being phased out)
AES	128, 192, or 256 bits	Block cipher	Current standard
RC4	40 to 2048 bits	Stream cipher	Deprecated (insecure)
Blowfish	32 to 448 bits	Block cipher	Legacy

Asymmetric Encryption (Public/Private Key Pair)

Uses a key pair: public key encrypts, private key decrypts (or vice versa for digital signatures). Slower but solves key distribution.

Algorithm	Key Size	Primary Use
RSA	2048+ bits	Encryption and digital signatures
DSA	2048+ bits	Digital signatures only
ECC	256+ bits	Encryption and signatures (smaller keys, same strength)
Diffie-Hellman	2048+ bits	Key exchange only (not encryption)

Hashing Algorithms (One-Way)

Produce a fixed-length digest. Cannot be reversed. Used for integrity verification and password storage.

Algorithm	Output Size	Status
MD5	128 bits	Broken (collision attacks)
SHA-1	160 bits	Deprecated
SHA-256	256 bits	Current standard
SHA-3	224 to 512 bits	Latest standard

Key Concepts

Digital Signature: Hash the message, then encrypt the hash with the sender's private key
Digital Certificate: Binds a public key to an identity, issued by a Certificate Authority (CA)
PKI: The infrastructure (CAs, registration authorities, certificates) that manages public keys
Key Escrow: A copy of the encryption key held by a trusted third party

Encryption Algorithms Reference