Practice tests · 40 items

Cryptography, PKI & TLS practice test

Hashes, MACs, authenticated encryption, public-key cryptography and signatures, how TLS 1.3 works, certificates and chains of trust, Certificate Transparency, mutual TLS, and key management with KMS and HSMs, through to protecting model weights. The pool for this topic holds 11 easy, 18 medium and 11 hard items. Each answer comes with its reasoning and a link to the question or concept page it was drawn from.

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Questions

11 in this pool · about 7 min

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Sample items with answers

easy · sample

Which operation can anyone reverse without a key?

AES-GCM encryption of a message under a 256-bit key

✓Base64 encoding

An Ed25519 signature produced with a private signing key

A SHA-256 hash computed over the contents of a file

Encoding only changes representation; anyone can decode Base64. Encryption needs the key to reverse, a hash cannot be reversed at all, and a signature is verified rather than reversed. Treating encoded secrets as protected is a common configuration mistake.

easy · sample

A download page shows a file and its SHA-256 hash, both served by the same web server. What does checking the hash protect against?

✓Accidental corruption in transit, but not an attacker who controls the server

Any attacker, because SHA-256 cannot be forged by anyone without the publisher's key

Malware inside the file, because a hash detects malicious code

Eavesdroppers, because a hash keeps the file's contents confidential

A hash has no key. An attacker who controls the server replaces the file and publishes the new hash beside it. A hash only proves integrity when it arrives through a channel the attacker cannot change, such as a signed manifest.

After the test

Choosing from options is easier than reasoning it out in front of a panel. These pages make you reason it out: