<P> In cryptography, a PKI is an arrangement that binds public keys with respective identities of entities (like people and organizations). The binding is established through a process of registration and issuance of certificates at and by a certificate authority (CA). Depending on the assurance level of the binding, this may be carried out by an automated process or under human supervision . </P> <P> The PKI role that assures valid and correct registration is called a registration authority (RA). An RA is responsible for accepting requests for digital certificates and authenticating the entity making the request . In a Microsoft PKI, a registration authority is usually called a subordinate CA . </P> <P> An entity must be uniquely identifiable within each CA domain on the basis of information about that entity . A third - party validation authority (VA) can provide this entity information on behalf of the CA . </P> <P> Public key cryptography is a cryptographic technique that enables entities to securely communicate on an insecure public network, and reliably verify the identity of an entity via digital signatures . </P>

Which of the following levels of algorithms does public key infrastructure (pki) use