What is created by encrypting a hash value with a private key?

• A. Public key
• B. Encryption key
• C. Digital signature
• D. Password hash

Answer: (C)

When a hash value is encrypted with a private key, it leads to the creation of a digital signature. The process of generating a digital signature involves first hashing a message or document to create a fixed-size string that represents the message's content. Encrypting this hash with the signer's private key produces a digital signature that serves two primary purposes: authentication and integrity.

The digital signature allows the recipient to verify that the signature was created by the holder of the private key (authenticity) and that the content has not been altered in transit (integrity). The recipient can decrypt the digital signature using the public key associated with the private key to recover the hash value. They can then hash the original message again and compare the two hash values; if they match, it confirms that the signature is valid.

This process highlights the significance of public and private key pairs in asymmetric encryption, where the private key is kept secret by the signer, and the public key is available for anyone to use for verification. Other options such as a public key, encryption key, or password hash do not encompass the properties and functionalities of what is produced through the described action of encrypting a hash with a private key.