key (tool for opening or locking something) / key; clue (important fact for solving something) / lock

(computing) key / (music) key

(cryptography) secret key

keyhole

(cryptography) key exchange - an exchange of peers' keys at initialization phase of connection.

(literally) sniff around / (figuratively) nose around, snoop

counterclockwise swastika

a corner bracket, either of the pair of brackets 「」, serving as a quotation mark in Chinese and Japanese orthography

spare key

(Internet slang) protected account (on social media, especially Twitter and Instagram)