What is used to authenticate the owner of a public key?

Public-key cryptography is based on the concept of a key pair, which consists of a public key and a private key. Data that has been encrypted with a public key can be decrypted only with the corresponding private key. Conversely, data that has been encrypted with a private key can be decrypted only with the corresponding public key.

The owner of the key pair makes the public key available to anyone, but keeps the private key secret.

A certificate verifies that an entity is the owner of a particular public key.

Certificates that follow the X.509 standard contain a data section and a signature section. The data section includes such information as:

• The Distinguished Name of the entity that owns the public key

• The Distinguished Name of the entity that issued the certificate

• The period of time during which the certificate is valid

• The public key itself

You can obtain a certificate from a Certificate Authority (CA) such as VeriSign. Alternately, you can create a self-signed certificate, in which the owner and the issuer are the same.

An organization that issues certificates can establish a hierarchy of CAs. The root CA has a self-signed certificate. Each subordinate CA has a certificate that is signed by the next highest CA in the hierarchy. A certificate chain is the certificate of a particular CA, plus the certificates of any higher CAs up through the root CA.

Keys, digital certificates, and trusted certificate authorities establish and verify the identities of applications.

SSL uses public key encryption technology for authentication. In public key encryption, a public key and a private key are generated for an application. The data encrypted with the public key can be decrypted only with corresponding private key. Similarly, the data encrypted with the private key can be decrypted only by using the corresponding public key. The private key is password-protected in a key database file. Only the owner can access the private key to decrypt messages that are encrypted with the corresponding public key.

A signed digital certificate is an industry-standard method of verifying the authenticity of an entity, such as a server, a client, or an application. To ensure maximum security, a third-party certificate authority provides a certificate. A certificate contains the following information to verify the identity of an entity:Organizational informationThis certificate section contains information that uniquely identifies the owner of the certificate, such as organizational name and address. You supply this information when you generate a certificate with a certificate management utility.Public keyThe receiver of the certificate uses the public key to decipher encrypted text that is sent by the certificate owner to verify its identity. A public key has a corresponding private key that encrypts the text.Certificate authority's distinguished nameThe issuer of the certificate identifies itself with this information.Digital signatureThe issuer of the certificate signs it with a digital signature to verify its authenticity. The corresponding CA certificate compares the signature to verify that the certificate is originated from a trusted certificate authority.

Reflection for Secure IT uses public key host authentication by default. The server automatically generates a new host key (or migrates an existing host key) during installation. The default key is an RSA 2048-bit key.

Public key cryptography uses a mathematical algorithm with a public/private key pair to encrypt and decrypt data. One of the keys is a public key, which can be freely distributed to communicating parties, and the other is a private key, which should be kept secure by the owner of the key. Data encrypted with the private key can be decrypted only with the public key; and data encrypted with the public key can be decrypted only with the private key.

When keys are used for authentication, the party being authenticated creates a digital signature using the private key of a public/private key pair. The recipient must use the corresponding public key to verify the authenticity of the digital signature. This means that the recipient must have a copy of the other party's public key and trust in the authenticity of that key.

How it Works

When public key authentication is used for host authentication, the following sequence of events takes place.

1. The Secure Shell client initiates a connection.

2. The server sends its public key to the client.

3. The client looks for this key in its trusted host key store.

   Finds the host key, and the client copy matches the key sent by the server

   Authentication proceeds to the next step.

   Does not find the host key

   The client displays a message that the host is unknown and provides a fingerprint of the host key. If the client is configured to allow the user to accept unknown keys (the default), the user can accept the key, and authentication proceeds to the next step.

   If strict host key checking is enforced, the client ends the connection.

   Finds a host key, and the client copy doesn't match the key sent by the server

   The client displays a warning that the key doesn't match the existing key and displays the fingerprint of the key sent by the server. If the client is configured to allow the user to accept unknown keys (the default), the user can accept the new key.

   If strict host key checking is enforced, the client ends the connection.

4. The server creates a digital signature based on the challenge message. To do this, the server independently computes the message hash, and then encrypts the computed hash using its private key. The server attaches this digital signature to the original challenge and returns this signed message to the client.

5. The client decrypts the signature using the public key and compares the hash with its own computed hash. If the values match, host authentication is successful.

   Which key is used for authentication?

   The A-key is a 64-bit secret number that is the permanent key used by the authentication calculations in both the MS and the AC. The A-key is permanently installed into the MS and is securely stored at the AC in the network when a new subscription is obtained.

   What is public private key authentication?

   Public key cryptography uses a mathematical algorithm with a public/private key pair to encrypt and decrypt data. One of the keys is a public key, which can be freely distributed to communicating parties, and the other is a private key, which should be kept secure by the owner of the key.

   How does public key authentication work?

   The most common means of authentication is via SSH asymmetric key pairs. The server uses the public key to encrypt a message and send it to the client. If the client has the correct private key, they can decrypt the message and send it back to the server for verification.

   Does public key provide authentication?

   In a digital signature, the private key has the responsibility for digitally signing documents and authenticating the identity. The public key is meant to verify the signature and verify the authentication.