SSH-Keygen Online Algorithm RSA DSA ECDSA
RSA Key Size 1024 2048 4096
ECDSA Key Size 256 384 521
DSA Key Size 512 576 640 704 768 832 896 960 1024 2048

Any private key value that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen, for extra security run this software on your network, no cloud dependency
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Generate an RSA SSH keypair with a 4096 bit private key
ssh-keygen -t rsa -b 4096 -C "RSA 4096 bit Keys"

Generate an DSA SSH keypair with a 2048 bit private key
ssh-keygen -t dsa -b 1024 -C "DSA 1024 bit Keys"
Generate an ECDSA SSH keypair with a 521 bit private key
ssh-keygen -t ecdsa -b 521 -C "ECDSA 521 bit Keys"

Generate an ed25519 SSH keypair- this is a new algorithm added in OpenSSH.
ssh-keygen -t ed25519

Extracting the public key from an RSA keypair
openssl rsa -pubout -in private_key.pem -out public_key.pem
Extracting the public key from an DSA keypair
openssl dsa -pubout -in private_key.pem -out public_key.pem

Copy the public key to the server
The ssh-copy-id command
ssh-copy-id user@hostname copies the public key of your default identity (use -i identity_file for other identities) to the remote host

SSH Running on different port

ssh-copy-id -i "user@hostname -p2222"

-i switch defaults to ~/.ssh/, if you want another key, put the path of the key after

Converting keys between openssl and openssh
Extract Public key from the certificate
openssl x509 -in cert.pem -noout -pubkey >pubkey.pem
cat pubkey.pem
-----END PUBLIC KEY-----
Use the following command to convert it to authorized_keys entry
$ ssh-keygen -i -m PKCS8 -f pubkey.pem
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQDROqW94oqVzYwW8Sa5cmIsYGxjW3gwvi6JEAMZJmWdz7tSC/eH4wKOSTA4qI52w2jyTgpIEgbkZxB8pg453XvbngfjPMhhAV0XSy3s1wUFGPWlumctOvaowxXf60y7h5zsDTSTHzO5d2agAk6Aix95c+RHFZaJz0BUhL74flCLavttQVf5yoWzJQ==