$ java -cp classes Mistakes      (25.0.5+8-LTS)
== 1. Same info for two purposes: the 'two' keys are one key
PASS  encryption key == MAC key when info is the same
PASS  distinct info labels give distinct keys
== 2. Gluing fields together without a delimiter: tenant 'ab' + 'c' collides with 'a' + 'bc'
PASS  naive concatenation collides
PASS  length-prefixed fields (Tenants.info) do not collide
== 3. Salt: leaving it out is the same as HashLen zero bytes, and a salt is not a secret
PASS  no salt == 32 zero bytes (SHA-256)
PASS  a different salt changes every output, so a salt change is a key change
== 4. Asking for more than 255 * HashLen bytes
length 8160 -> ok (8160 bytes)
length 8161 -> InvalidAlgorithmParameterException: The specified SunJCE provider does not support this input
== 5. Deriving a key from a low-entropy secret (a 4-digit PIN)
HKDF-derived key: attacker finds PIN 4821 after 4822 guesses
PASS  PBKDF2 (600000 iterations) is at least 1000 times slower per guess than HKDF
ALL CHECKS PASSED
exit=0