How to create public and private key with openssl?

Question

My question is how to create a public key and private key with OpenSSL in windows and how to put the created public key in .crt file and the private one in .pcks8 file in order to use this two keys to sign a SAML assertion in Java?

Thanks in advance.

Answer 1

You can generate a public-private keypair with the genrsa context (the last number is the keylength in bits):

openssl genrsa -out keypair.pem 2048

To extract the public part, use the rsa context:

openssl rsa -in keypair.pem -pubout -out publickey.crt

Finally, convert the original keypair to PKCS#8 format with the pkcs8 context:

openssl pkcs8 -topk8 -inform PEM -outform PEM -nocrypt -in keypair.pem -out pkcs8.key