OpenSSH Private Key to RSA

openssh2rsa

# OpenSSH Private Keys have a specific format
# It cannot be read by openssl and gives that error : 
# Could not read private key from id_rsa
# I also tried with ssh-keygen 
# > ssh-keygen -if id_rsa -m PEM
# That gives 
# > do_convert_from_pem: unrecognised raw private key format

# The solution is to use ssh-keygen and to change the passphrase : 
ssh-keygen -p -N "" -m pem -f id_rsa