What specific cryptographic technique uses a pair of keys, one public and one private, for encryption and decryption, and is also used for digital signatures?

The specific cryptographic technique that uses a pair of keys, one public and one private, for encryption and decryption, and is also used for digital signatures, is called Public-Key Cryptography, also known as Asymmetric Cryptography. This method relies on two mathematically linked keys: a public key and a private key. A public key is openly distributed and can be shared with anyone; it is used for encrypting data or for verifying digital signatures. The corresponding private key is kept secret by its owner and is used for decrypting data that was encrypted with the matching public key, or for creating digital signatures. When used for encryption, a sender takes data and encrypts it using the recipient's public key. The encrypted data can then only be decrypted by the recipient using their unique private key. For example, if Alice wants to send a secret message to Bob, Alice uses Bob's public key to encrypt the message. Only Bob, possessing his private key, can decrypt and read the message. When used for digital signatures, the process reverses the key roles. The owner of the keys uses their private key to create a digital signature for a piece of data, typically a cryptographic hash of the data. A digital signature provides assurance of the data's integrity and the signer's authenticity. For instance, if Bob wants to digitally sign a document, he uses his private key to create the signature. Anyone can then use Bob's public key to verify that the signature was indeed created by Bob (proving authenticity) and that the document has not been altered since it was signed (proving integrity). This dual functionality is fundamental to secure communication and transaction verification over untrusted networks.