ssh-keygen
authentication key generation, management and conversion
ssh-keygen [-q] [-b bits] -t type [-N new_passphrase] [-C comment] [-f output_keyfile]
ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile]
ssh-keygen -i|e [-f keyfile]
import|export
ssh-keygen -y [-f keyfile]
(yank private OpenSSH, output public key)
ssh-keygen -c [-P passphrase] [-C comment] [-f keyfile]
ssh-keygen -l [-f keyfile]
(list fingerprint)
ssh-keygen -B [-f keyfile]
(show bubblebabble)
ssh-keygen -F hostname [-f known_hosts_file] [-l]
(find host)
ssh-keygen -H [-f known_hosts_file]
(hash it)
ssh-keygen -R hostname [-f known_hosts_file]
(remove host)
ssh-keygen -D|U reader
download|Upload to reader
ssh-keygen -r hostname [-f input_keyfile] [-g]
(reveal fingerprint)
Generates, manages and converts authentication keys for
- Users runs this to create their authentication key for use with ssh.
- groups for use in Diffie-Hellman group exchange (DH-GEX).
- host keys for
/etc/rc
and dnssec.
Generates the key and asks for a file for the private key, the public key is stored in a file with .pub
appended.
WARNING: With SSH keys, if someone gains access to your computer, they also gain access to every system that uses that key.
To add an extra layer of security, add a passphrase .
Use ssh-agent to securely save the passphrase so you don't have to reenter it.
Passphrase may be a string of arbitrary length, changed using -p
.
Similar to a password can be a phrase of words, punctuation, numbers, whitespace, or any string.
For RSA1 keys a comment field helps identify the key, changed using -c
.
-t RSA|DSA|ECDSA
Ed25519| RSA vs DSA (when in doubt pick DSA IMHO ) Digital Signature Algorithm vs Ron Rivest, Adi Shamir, and Leonard Adleman.
Gory details can be found here
| -a rounds When saving PrivateKey, KDF rounds (key derivation function). default: 16.
| -b bits in the key. RSA minimum 768, default: 2048 . DSA 1024, ECDSA 256| 384 | 521
| -C comment -c for RSA1
change comment.
| -D reader -U reader Download the RSA public key to a smartcard in reader.
Upload an existing RSA private key into the smartcard in reader.
| -e export key in RFC 4716 SSH Public Key File Format to stdout ssh-keygen -e
Enter file in which the key is (/Volumes/DATA/username/.ssh/id_rsa):
---- BEGIN SSH2 PUBLIC KEY ----
Comment: "2048-bit RSA, converted by username@smacpro from OpenSSH"
AAAAB3NzaC1yc2EAAAADAQABAAABAQDWb/oxOZjP0NE9x3WXylzw8qdUMExmw776i+84mJ
jzBOM8skMaR2j4xXD+Dt3UFS1ZUzh4oRkFIx7LR6nKt5xm4Yd5uZVB/Yj3K7b6FDjSoJcO
ld02toxP46NT87dYIhNazH2J0kDW9tym5thxbUqC3gltxGJmuJo9WT6ySLqqC5HyPF5i/v
g/b00FBldllze9Wb6o2nLV9i7aeADMY3prFxPV1w33qOxGJGQTLwYvRmu893TVuLCJj9IK
ptJp/n+SellVr0pf9aNimyfDb9Sq3HFpOZGxMwgWjsyWx4Xjwy9r66bvuznfYqECoJKvCS
yEJMFUGpSx0y0v8dUl9C1T
---- END SSH2 PUBLIC KEY ----
| -F hostname Find hostname in known_hosts
Useful to find hashed host names or addresses and may also be used with -H
| -H Hash known_hosts the original is moved to .old .
| -R hostname Removes keys from known_hosts file useful to delete hashed hosts
| -i Reads an unencrypted private key file or RFC4716 Public Key and outputs an OpenSSH key.
| -f filename key file.
| -l list fingerprint of specified public key file.
With -v , an ASCII art representation of the key output:
| -B file Show the bubblebabble digest
| -p file change the passphrase of a private key file.
Prompts for the file containing the private key, old passphrase, and new passphrase.
-N new‑passphrase |
| -P current-passphrase
| -q quite (Used by /etc/rc when creating a new key.)
| -r hostname | Reveal the SSHFP fingerprint Resource Record for the specified public key file. More at StackExchange
Default .ssh/id_rsa > ssh-keygen -r midphase.com
no keys found.
DNS record sha-256 is the type, dynu.com/Resources/DNS-Records/SSHFP-Record
Algorithm
- - RSA. RSA (Rivest-Shamir-Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission.
- - DSA. The Digital Signature Algorithm (DSA) is a Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem.
- - ECDSA. The Elliptic Curve Digital Signature Algorithm (ECDSA) offers a variant of the Digital Signature Algorithm (DSA) which uses elliptic curve cryptography.
RFC6594 SHA-256 Algorithm with RSA, Digital Signature Algorithm (DSA), and Elliptic Curve DSA (ECDSA) in SSHFP Resource Records
- - Ed25519. Ed25519 is the EdDSA signature scheme using SHA-512 (SHA-2) and Curve25519.
See /etc/ssh/ssh_hosts_*.key used by the sshd service.
| -g Use generic DNS format when outputing fingerprint resource records using -r
| -y yank private file and output public key to stdout.ssh-keygen -y
Enter file in which the key is (/Volumes/DATA/username/.ssh/id_rsa):
ssh-rsa AAAAB3NzaC1yc2EAAAADAQAB
SellVr0pf9aNixxxxx9Sq3HFpOZGmMwnfYqECoJKvCSyEJMFUGpSx0y0v8dUl9C1T
| | | | | | | | | | | | | | | | | | | |
> ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/Volumes/DATA/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Volumes/DATA/username/.ssh/id_rsa.
Your public key has been saved in /Volumes/DATA/username/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:oTvL+IaG8Hpe1D862lBRr7RMsqfEZtMaUymJVX/OLdY username@smacpro
The key's randomart image is:
+---[RSA 2048]----+
| ..o |
| o o + |
| . = * o . |
| o % + + o |
| . & S = E |
|. . = X . . |
| . o..= o |
| +.==o+ . |
|.+..o+*. |
+----[SHA256]-----+
> ssh-keygen -B
Enter file in which the key is (/Volumes/DATA/username/.ssh/id_rsa):
2048 xugel-tymes-mopal-vyzoz-xxxxx-yyyyy-zzzzz-fcyc-kehip-nelef-vuxyx username@clienthost (RSA)
> sh-keygen -l
Enter file in which the key is (/Volumes/DATA/username/.ssh/id_rsa):
2048 SHA256:oTvL+xxxxxxxxxx62yyyyyyyyyyEZtMaUymJVX/OLdY username@clienthost (RSA)/pre>
Next copy the key to the server see ssh
FILES
~/.ssh/identity
version 1 RSA authentication identity of the user. Must be not be readable by
by group or others. It is possible to specify a passphrase when generating the key which is
used to encrypt the private part using 3DES. Not automatically accessed by ssh-keygen
but is the default file for the private key. Read by ssh at login
| ~/.ssh/identity.pub version 1 RSA public key . Add to ~/.ssh/authorized_keys
| ~/.ssh/id_dsa
version 2 DSA authentication identity of the user. Must be not be readable by
by group or others. It is possible to specify a passphrase when generating the key is
used to encrypt the private part of this file using 3DES. Not automatically accessed by ssh-keygen
but default is the file for the private key. Read by ssh at login
made.
| ~/.ssh/id_dsa.pub version 2 DSA public key. Add to ~/.ssh/authorized_keys
| ~/.ssh/id_rsa
version 2 RSA authentication identity of the user.
Must be not be readable by by group or others. A passphrase when generating the key used to encrypt the private part of this file using 3DES. Not automatically accessed by ssh-keygen
default file for the private key. Read by ssh at login
| ~/.ssh/id_rsa.pub
version 2 RSA public key . Added to ~/.ssh/authorized_keys
| /etc/ssh/moduli for DH-GEX. See moduli
| | | | | | | |
ssh-agent
ssh-agent [-c | -s ] [-Dd] [-a bind_address] [-E fingerprint_hash ] [-P pkcs11_whitelist ] [-t lifetime]
[command [arg …]]
ssh-agent [-c | -s] -k
Outputs private keys used for public key authentication used when logging in to other machines using ssh.
Started in the beginning of a login session or an X-session .
Keys are added or removed using ssh-add (see AddKeysToAgent in ssh_config(5) for details) ssh-add(1).
-a bind_address Bind to socket. Default $TMPDIR/ssh-XXXXXXXXXX/agent.ppid .
| -D Don't fork, Foreground .
| -d debug
| -E md5|sha256 default sha256 .
| -k Kill the current agent from $SSH_AGENT_PID
| -P pkcs11_whitelist
a pattern-list of acceptable paths for PKCS#11 shared libraries that may be added using -s to
ssh-add(1).
Default: allow loading PKCS#11 libraries from /usr/lib/*,/usr/local/lib/* .
PKCS#11 libraries that do not match the whitelist will be refused. See PATTERNS in ssh_config(5) for pattern-list syntax.
| -c Generate C-shell commands on stdout. default if SHELL looks like it's a csh style of shell.
| -s Generate Bourne shell commands on stdout. default if SHELL does not look like it's a csh style of shell.
| -t lifetime maximum lifetime of identities added to the agent in
seconds or in a time format specified in sshd_config(5).
A lifetime specified for an identity with ssh-add overrides this value.
Default forever.
| | | | | | | | | |
With command
executed as a subprocess of the agent. When the command dies, so does the agent.
-
agent starts a new subcommand into which some environment variables are exported, eg ssh-agent xterm &.
- agent outputs the needed shell commands
(either sh(1) or csh(1) syntax can be generated) which can be evaluated in the calling shell, eg eval `ssh-agent -s` for
Bourne-type shells such as sh(1) or ksh(1) and eval `ssh-agent -c` for csh(1) and derivatives.
$SSH_AGENT_PID
holds the agent's process ID.
The agent exits when the command given on the command line terminates.
Example:
> ssh-agent
SSH_AUTH_SOCK=/var/folders/rr/jvwb6c9j2h18lzc28kzws_940000gn/T//ssh-oZQicexUeNIT/agent.91702; export SSH_AUTH_SOCK;
SSH_AGENT_PID=91703; export SSH_AGENT_PID;
echo Agent pid 91703
FILES
$TMPDIR/ssh-XXXXXXXXXX/agent.ppid>
UNIX-domain sockets used to contain the connection to the authentication agent. These sockets should only be
readable by the owner. The sockets should get automatically removed when the agent exits.
SEE ALSO
ssh, ssh-add(1), ssh-agent(1), moduli(5), sshd(8)