Who keeps private key in asymmetric key cryptography?
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: "public keys" which may be disseminated widely, and "private keys" which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.
Who keeps private key in asymmetric key cryptography for encryption?
the owner the receiver
Public-key cryptography
Robust authentication is also possible. A sender can combine a message with a private key to create a short "digital signature" on the message. Anyone with the sender's corresponding public key can combine the same message and the supposed digital signature associated with it to verify whether the signature was valid, i.e. made by the owner of the corresponding private key.
Who keeps private key in asymmetric key cryptography for authentication?
the owner sender
Public-key cryptography
Public-key cryptography
https://en.wikipedia.org/wiki/Public-key%20cryptography
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys. Each pair consists of a public key (which may be known to others) and a private key (which may not be known by anyone except the owner). The generation of such key pairs depends on cryptographic algorithms which are based on mathematical problems termed one-way functions. Effective security requires keeping the private key private; the public key can be openly distributed without compromising security.
Public-key cryptography
With public-key cryptography, robust authentication is also possible. A sender can combine a message with a private key to create a short digital signature on the message. 
Public-key cryptography
Public key encryption, in which a message is encrypted with the intended recipient's public key. For properly chosen and used algorithms, messages cannot in practice be decrypted by anyone who does not possess the matching private key, who is thus presumed to be the owner of that key and so the person associated with the public key. This can be used to ensure confidentiality of a message.
Public-key cryptography
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys. Each pair consists of a public key, which may be known to others, and a private key, which may not be known by anyone except the owner. The generation of such key pairs depends on cryptographic algorithms which are based on mathematical problems termed one-way functions. For encryption, the receiver keeps private key and in authentication the sender keeps the private key.