Which type of cryptography does SSL, IKE and PGP belongs to?

Secret key (symmetric) cryptography uses a single shared key for both encryption and decryption; while SSL and IKE do negotiate symmetric ciphers for bulk data, their defining mechanism for key agreement and authentication is asymmetric public key operations.

Hash algorithms are one-way functions that produce a fixed-length digest from input data and are not classified as a cryptographic system alongside symmetric or asymmetric encryption.

Digest refers specifically to the fixed-length output value produced by a hash function, and is not a category of cryptographic system that SSL, IKE, or PGP would be classified under.

Public key cryptography uses a public and private key pair where data encrypted with one key can only be decrypted with the other. SSL/TLS uses RSA or ECDH for asymmetric key exchange and certificate-based server authentication, IKE uses Diffie-Hellman public key exchange to establish shared secrets for IPsec tunnels, and PGP uses RSA or DSA for digitally signing and encrypting messages - making asymmetric public key cryptography the common foundation of all three.