Introduction into Ed25519
OpenSSH 6.5 added support for Ed25519 as a public key type. It is using an elliptic curve signature scheme, which offers better security than ECDSA and DSA. At the same time, it also has good performance. This type of keys may be used for user and host keys. With this in mind, it is great to be used together with OpenSSH. In this article, we have a look at this new key type.
DSA or RSA
- After that, I also had to restart the ssh service: sudo service ssh restart – Alan May 24 '17 at 21:19 I had empty files for dsa, ecdsa and ed25519 that I had to delete for ssh-keygen -A to do anything – HeatfanJohn May 9 '18 at 22:23.
- Dec 31, 2018 Your host private key is locked using passphrase and when the ssh try to read it can't unlock it. You can unlock it manually and then point ssh to use the unlocked private key using the following command: openssl rsa -in privatekey.key -out unlockedprivatekey.key.
- SSH is a service which most of system administrators use for remote administration of servers. When you install a fresh system, then at the start of the ssh service, it generates the host keys for your system which later on used for authentication. But if due to some reason you need to generate the host keys, then the process is explained below.
Hi, to generate sshd host keys, for example in case of cloning a virtual linux instance, do the following steps: Checkout the key file names root@debdevt:# grep HostKey /etc/ssh/sshdconfig. Mar 29, 2014 Welcome to LinuxQuestions.org, a friendly and active Linux Community. You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features.
Many forum threads have been created regarding the choice between DSA or RSA. DSA is being limited to 1024 bits, as specified by FIPS 186-2. This is also the default length of ssh-keygen. While the length can be increased, it may not be compatible with all clients. So it is common to see RSA keys, which are often also used for signing. With Ed25519 now available, the usage of both will slowly decrease.
Configuring the server
Generate Ecdsa Ssh Key
The first thing to check is if your current OpenSSH package is up-to-date. You will need at least version 6.5 of OpenSSH.
Create SSH host keys
Change SSH configuration (server)
Next step is changing the sshd_config file. Add the new host key type:
HostKey /etc/ssh/ssh_host_ed25519_key
Remove any of the other HostKey settings that are defined.
Client Configuration
After configuring the server, it is time to do the client. We have to create a new key first. Make sure that your ssh-keygen is also up-to-date, to support the new key type. Note: the tilde (~) is an alias for your home directory and expanded by your shell.
Optional step: Check the key before copying it.
ssh-keygen -l -f ~/.ssh/id_ed25519
If that looks good, copy it to the destination host.
ssh-copy-id -i ~/.ssh/id_ed25519.pub michael@192.168.1.251
Then determine if we can log in with it.
$ ssh -i ~/.ssh/id_ed25519 michael@192.168.1.251 Enter passphrase for key ‘~/.ssh/id_ed25519’:
When using this newer type of key, you can configure to use it in your local SSH configuration file (~/.ssh/config). Defining the key file is done with the IdentityFile option.
Host [name]
HostName [hostname]
User [your-username]
IdentityFile ~/.ssh/id_ed25519
IdentitiesOnly yes
Insight: using -o
Normally you can use the -o option to save SSH private keys using the new OpenSSH format. It uses bcrypt/pbkdf2 to hash the private key, which makes it more resilient against brute-force attempts to crack the password. Only newer versions (OpenSSH 6.5+) support it though. For this key type, the -o option is implied and does not have to be provided. Also, a bit size is not needed, as it is always 256 bits for this key type.
Ssh Keys
Are you already using the new key type? Or other tips for our readers? Leave a comment.
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