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ssh-keygen is able to generate a key using one of three different digital signature algorithms. With the help of the ssh-keygen tool, a user can create passphrase keys for any of these key types. To provide for unattended operation, the passphrase can be left empty, albeit at increased risk.
Secure Shell (SSH) is a protocol allowing secure remote login to a computer on a network using public-key cryptography.SSH client programs (such as ssh from OpenSSH) typically run for the duration of a remote login session and are configured to look for the user's private key in a file in the user's home directory (e.g., .ssh/id_rsa).
ssh-add and ssh-agent, utilities to ease authentication by holding keys ready and avoid the need to enter passphrases every time they are used. ssh-keygen, a tool to inspect and generate the RSA, DSA and elliptic-curve keys that are used for user and host authentication. ssh-keyscan, which scans a list of hosts and collects their public keys.
This output would be produced by a ssh-keygen -r host.example.com. command on the target server by reading the existing default SSH host key (Ed25519). [5] With the OpenSSH suite, the ssh-keyscan utility can be used to determine the fingerprint of a host's key; using the -D will print out the SSHFP record directly. [6]
SSH operates as a layered protocol suite comprising three principal hierarchical components: the transport layer provides server authentication, confidentiality, and integrity; the user authentication protocol validates the user to the server; and the connection protocol multiplexes the encrypted tunnel into multiple logical communication channels.
In systems such as SSH, users can exchange and check fingerprints manually to perform key authentication. Once a user has accepted another user's fingerprint, that fingerprint (or the key it refers to) will be stored locally along with a record of the other user's name or address, so that future communications with that user can be ...
Since public-key algorithms tend to be much slower than symmetric-key algorithms, modern systems such as TLS and SSH use a combination of the two: one party receives the other's public key, and encrypts a small piece of data (either a symmetric key or some data used to generate it). The remainder of the conversation uses a (typically faster ...
Challenge-response authentication can help solve the problem of exchanging session keys for encryption. Using a key derivation function, the challenge value and the secret may be combined to generate an unpredictable encryption key for the session. This is particularly effective against a man-in-the-middle attack, because the attacker will not ...