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

key

a house / one's own home / a home, household / a family

to shut, to close

(telephony) a common Japanese telephone greeting: hello; used when answering the telephone / used to confirm that the person being addressed is listening, or to confirm if anyone is listening

(idiomatic) A piece of cake; an extremely simple thing, something trivial, a cinch, easy as pie.

朝飯前: A piece of cake; an extremely simple thing.

put away

forget oneself / be beside oneself

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