Advanced › Module 2 › Lesson 1
Symmetric Named
Symmetric literacy names AES, ChaCha20, modes (GCM, CBC), and key length — map concepts on YOUR $CRYPTO_LAB openssl demos before any solver work.
Visual · t28_symmetric_named
Symmetric literacy. $CRYPTO_LAB only. Original Cyberlium.
Opening
Same key encrypts and decrypts — literacy starts with primitive names and mode tradeoffs, not random script attacks on live traffic.
Symmetric primitives use one shared secret key: AES (128/256-bit), ChaCha20 stream cipher, and modes like GCM (authenticated encryption), CBC (needs careful padding — defender literacy only), and CTR. Key management and nonce uniqueness matter as much as algorithm choice. Cyberlium maps symmetric vocabulary on YOUR $CRYPTO_LAB openssl encrypt/decrypt demos with generated keys — never decrypt stranger ciphertext from production captures without scope. Next: Asymmetric Named.
1. Symmetric primitives (named)
AES: block cipher standard — use with GCM or CTR plus MAC for legacy patterns. ChaCha20-Poly1305: modern AEAD common in TLS 1.3. CBC: legacy mode; padding mistakes enable oracle-class bugs — name for defender literacy, do not exploit production.
On $CRYPTO_LAB, list three symmetric algorithms and one recommended mode each — demo keys only.
Command guide
Try these commands — Symmetric primitives (named)
═══ TOOLS & WEBSITES ═══ Browse / read these (authorized learning only — stay in YOUR lab / program scope)
Optional command
OpenSSL dgst — https://www.openssl.org/docs/manmaster/man1/openssl-dgst.html (hash literacy)
NIST SHA-256 — https://csrc.nist.gov/publications/detail/fips/180/4/final RFC 8446 — https://www.rfc-editor.org/rfc/rfc8446 (TLS 1.3 — hash in handshake context)
═══ INSTALL ═══
Linux (Debian/Ubuntu):
Command — copy this
sudo apt install openssl sudo apt install python3
macOS:
Command — copy this
brew install python3
Windows:
Command — copy this
choco install openssl
Download https://python.org/downloads/
═══ LINUX / macOS ═══
Command — copy this
export CRYPTO_LAB=${CRYPTO_LAB:-$HOME/cyberlium-lab/t28-crypto}
cat > "$CRYPTO_LAB/data/demo.txt" <<'EOF'
CYBERLIUM LAB DEMO — YOUR plaintext only
Message: cryptography literacy exercise 2026-08-22
Never hash or encrypt stranger production secrets without authorization
EOFCommand — copy this
openssl dgst -sha256 "$CRYPTO_LAB/data/demo.txt"
python3 -c "print('Hash YOUR demo.txt — SHA-256 integrity literacy')"Primary tools to practice this lesson: openssl, python3. Reference sites: OpenSSL dgst (https://www.openssl.org/docs/manmaster/man1/openssl-dgst.html); NIST SHA-256 (https://csrc.nist.gov/publications/detail/fips/180/4/final); RFC 8446 (https://www.rfc-editor.org/rfc/rfc8446). Run every command in the box — install first, then the usage lines — only on YOUR lab / program scope.
2. Why symmetric literacy matters
Wrong mode (ECB on structured data) leaks patterns. Reused nonce in GCM breaks confidentiality. Static keys in config files are defender findings — students learn naming before touching real secrets.
Defenders prefer AEAD (GCM, ChaCha20-Poly1305) and envelope encryption with KMS — not DIY ciphers.
3. Lab boundary
Forbidden: claiming symmetric knowledge lets you decrypt any captured blob. Allowed: symmetric card — three algorithms, one mode note, $CRYPTO_LAB demo key source.
Ship: symmetric primitives card for YOUR lab demos. Next: Asymmetric Named.
4. What you ship: symmetric primitives card for $CRYPTO_LAB
Three algorithms with mode notes. $CRYPTO_LAB demo key source named. NO production ciphertext. chmod 600.
5. What you record before the next lesson
Date. Symmetric card. $CRYPTO_LAB named. File t28-m02-l01-symmetric-named.txt chmod 600.
6. Wrong vs right: prod crypto oracles vs CTF toys
Worked failure — same MSF word, opposite target. Right never needs a café Wi-Fi or classmate laptop.
Wrong
Decrypt production traffic with guessed keys. Use ECB for real projects because tutorial did.
Right
Write symmetric primitives card for YOUR $CRYPTO_LAB openssl demos. Next: Asymmetric Named.
Mission: name symmetric primitives on YOUR lab
1) Name AES, ChaCha20, and one legacy mode. 2) Note why GCM is preferred over bare CBC. 3) Record $CRYPTO_LAB demo key source. 4) chmod 600.
Stuck? Ask Cyberlium AI Mentor
AEAD = confidentiality + integrity in one step — default recommendation for new code.
Knowledge Check
APPLY: Symmetric literacy means:
Multiple choice
Knowledge Check
APPLY: True or False: AES-GCM provides authenticated encryption.
True or False
Knowledge Check
APPLY: Symmetric literacy supports:
Multiple choice