Key import/export may be private key import/export, but it also may be public key import/export.

Here, key doesn't mean private key.
Use of 密钥 is good.

Key may be private key, but it also may be public key.
Use of 密钥 is good.

Key doesn't mean private key, here.
Use of 密钥 is good.

Actually, here, it means private key (by the context).
Use of 密钥 is OK, but technically speaking, Use of 私钥 is better.

Command history means: https://zh.wikipedia.org/wiki/%E5%91%BD%E4%BB%A4%E8%A1%8C%E5%8E%86%E5%8F%B2%E8%AE%B0%E5%BD%95