DOKK / manpages / debian 12 / dropbear-bin / dropbearkey.1.en
dropbearkey(1) General Commands Manual dropbearkey(1)

dropbearkey - create private keys for the use with dropbear(8) or dbclient(1)

dropbearkey -t type -f file [-s bits] [-y]

dropbearkey generates a RSA, DSS, ECDSA, or Ed25519 format SSH private key, and saves it to a file for the use with the Dropbear client or server. Note that some SSH implementations use the term "DSA" rather than "DSS", they mean the same thing.

Type of key to generate. Must be one of rsa ecdsa ed25519 or dss.
Write the secret key to the file file. For client authentication ~/.ssh/id_dropbear is loaded by default
Set the key size to bits bits, should be multiple of 8 (optional).
Just print the publickey and fingerprint for the private key in file.

The program dropbearconvert(1) can be used to convert between Dropbear and OpenSSH key formats.

Dropbear does not support encrypted keys.

generate a host-key:
# dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key

extract a public key suitable for authorized_keys from private key:
# dropbearkey -y -f id_rsa | grep "^ssh-rsa " >> authorized_keys

Matt Johnston (matt@ucc.asn.au).
Gerrit Pape (pape@smarden.org) wrote this manual page.

dropbear(8), dbclient(1), dropbearconvert(1)

https://matt.ucc.asn.au/dropbear/dropbear.html