Cryptography

Symmetric, asymmetric, and hashing algorithms compared for certification exams.

Current Legacy Deprecated

Symmetric Encryption

Algorithm	Type	Key Size	Block Size	Use Case	Status
AES	Block	128 / 192 / 256-bit	128-bit	Bulk encryption, disk encryption, TLS, Wi-Fi (WPA2/WPA3)	Current
ChaCha20	Stream	256-bit	N/A (stream)	TLS 1.3, mobile devices, WireGuard VPN	Current
3DES (Triple DES)	Block	112 / 168-bit effective	64-bit	Legacy financial systems, backward compatibility	Legacy
DES	Block	56-bit	64-bit	Historical — easily brute-forced, do not use	Deprecated
Blowfish	Block	32–448-bit	64-bit	Legacy applications, bcrypt password hashing	Legacy
Twofish	Block	128 / 192 / 256-bit	128-bit	AES finalist — used in some open-source tools	Current
RC4	Stream	40–2048-bit	N/A (stream)	Formerly WEP/SSL — known vulnerabilities	Deprecated

Asymmetric Encryption

Algorithm	Type	Key Size	Use Case	Status
RSA	Public Key	2048 / 3072 / 4096-bit	Digital signatures, key exchange, TLS certificates	Current
ECC (ECDSA/ECDH)	Elliptic Curve	256 / 384 / 521-bit	TLS, SSH, mobile/IoT (smaller keys, same strength)	Current
Diffie-Hellman (DH)	Key Exchange	2048+ bit	Key exchange — establishes shared secret over insecure channel	Current
ECDHE	Ephemeral Key Exchange	256+ bit	TLS perfect forward secrecy — new key per session	Current
DSA	Digital Signature	1024 / 2048 / 3072-bit	Legacy digital signatures — largely replaced by ECDSA	Legacy
ElGamal	Public Key	2048+ bit	GPG/PGP encryption	Legacy

Hashing & Key Derivation

Algorithm	Output Size	Speed	Use Case	Status
SHA-256	256-bit	Fast	TLS, code signing, blockchain, file integrity	Current
SHA-384	384-bit	Fast	TLS 1.2+, government systems	Current
SHA-512	512-bit	Fast	File integrity, high-security applications	Current
SHA-3 (Keccak)	224–512-bit	Moderate	Next-gen standard — alternative to SHA-2 family	Current
SHA-1	160-bit	Fast	Legacy git commits — collision attacks demonstrated	Deprecated
MD5	128-bit	Very Fast	Legacy checksums only — trivially broken for security	Deprecated
bcrypt	184-bit	Intentionally Slow	Password hashing — adaptive cost factor	Current
Argon2	Configurable	Intentionally Slow	Password hashing — memory-hard, winner of PHC	Current
PBKDF2	Configurable	Intentionally Slow	Password hashing, key derivation — NIST approved	Current
HMAC	Varies (uses underlying hash)	Fast	Message authentication — combines hash with secret key	Current