The best replacement for private key is public key.

The best alternatives to private key are rated as following:
★★★★★  public key
★★★  secret key
★★  public key encryption
★  foreign key
★  certificate
★  csr
  public

Your alternative for private key is not listed? Suggest!
Speaking about private key, one probably shouldn't forget about ssh.

Other search terms related to private key and their ratings are:
★★★★★ ssh
★★★★ openssl
★★★ ssl certificate
★★ keytool
★★ csr
★ certificate
You have in mind a companion for private key and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of private key in all years. Click on graph for more.
private key
public key
secret key