What is a Private Key?

• A. A key that is usually used to decrypt data.
• B. A key used to encrypt data for public distribution.
• C. A public key.
• D. A password.

Answer: (A)

In public-key cryptography, you work with a pair of keys: a private key that stays secret and a public key that can be shared. The private key’s primary role is to decrypt data that was encrypted with the matching public key. It can also be used to create digital signatures, proving something came from you without revealing that secret. That combination of duties—decrypting data secured with the public key (and signing) —is why describing it as a key usually used to decrypt data is the best fit among the options. The public key, not the private, is the one you share to encrypt data for others or to verify signatures. A password isn’t a cryptographic key in this context.