Generating local key pairs
About local key pairs
The DSA, ECDSA, or RSA key pairs on the SSH server are required for generating the session keys and session ID in the key exchange stage. They can also be used by a client to authenticate the server. When a client authenticates the server, it compares the public key received from the server with the server's public key that the client saved locally. If the keys are consistent, the client uses the locally saved server's public key to decrypt the digital signature received from the server. If the decryption succeeds, the server passes the authentication.
To support SSH clients that use different types of key pairs, generate DSA, ECDSA, and RSA key pairs on the SSH server.
RSA key pairs—The SSH server generates a server key pair and a host key pair for RSA. The RSA server key pair is only used in SSH1 to encrypt the session key for secure transmission of the session key. It is not used in SSH2, because no session key transmission is required in SSH2.
DSA key pair—The SSH server generates only one DSA host key pair. SSH1 does not support the DSA algorithm.
ECDSA key pair—The SSH server generates only one ECDSA host key pair.
Restrictions and guidelines
Local DSA, ECDSA, and RSA key pairs for SSH use default names. You cannot assign names to the key pairs.
If the device does not have RSA key pairs with default names, it automatically generates one RSA server key pair and one RSA host key pair when SSH starts. Both key pairs use their default names. The SSH application starts when you execute an SSH server command on the device.
The key modulus length must be less than 2048 bits when you generate the DSA key pair on the SSH server.
When you generate an ECDSA key pair, you can generate only a secp256r1 or secp384r1 ECDSA key pair.
The SSH server operating in FIPS mode supports only ECDSA and RSA key pairs. Do not generate a DSA key pair on the SSH server in FIPS mode.
Procedure
Enter system view.
system-view
Generate local key pairs.
public-key local create { dsa | ecdsa { secp256r1 | secp384r1 } | rsa }