Which of the following is an example of an asymmetric encryption implementation?

SHA1 is a one-way cryptographic hash function that produces a fixed-length digest and does not support any form of encryption or decryption.

PGP (Pretty Good Privacy) is an asymmetric encryption implementation that uses a recipient's public key to encrypt data, which can only be decrypted with the corresponding private key. It leverages asymmetric key exchange combined with a symmetric session key for efficiency, making it a canonical example of public-key cryptography in practice.

3DES (Triple DES) is a symmetric encryption algorithm that uses the same secret key for both encryption and decryption, not a public/private key pair.

MD5 is a one-way cryptographic hash function used for integrity verification, not an encryption scheme, and it has no concept of a key pair.