Which key is used to decrypt data or create digital signatures?

• A. Private Key
• B. Public Key
• C. Symmetric Cryptography
• D. Trapdoor Function

Answer: (A)

In public-key cryptography, there are two keys: one public and one private. The private key is kept secret and is used for operations that require ownership and proof, such as decrypting data that was encrypted with the public key and creating digital signatures. If someone encrypts a message with your public key, only your private key can decrypt it. Likewise, when you sign a message to prove it came from you, you do so with your private key, and others can verify the signature with your public key. The public key, by contrast, is used to encrypt data and to verify signatures, not to decrypt or sign. Symmetric cryptography uses a single shared secret key for both encryption and decryption and does not involve signing. A trapdoor function is a mathematical concept underlying these systems, not a specific key you use for decryption or signing.