More documentation about key size and OpenSSL compatibility
diff --git a/doc/compatibility.rst b/doc/compatibility.rst
index ab9e2e4..d82d1fa 100644
--- a/doc/compatibility.rst
+++ b/doc/compatibility.rst
@@ -27,24 +27,25 @@
:ref:`VARBLOCK <bigfiles>` encryption:
Python-RSA only, not compatible with any other known application.
+.. _openssl:
-Public keys from OpenSSL
+Interoperability with OpenSSL
--------------------------------------------------
-To get a Python-RSA-compatible public key from OpenSSL, you need the
-private key. Get the private key in PEM or DER format and run it
-through the ``pyrsa-priv2pub`` command::
+You can create a 512-bit RSA key in OpenSSL as follows::
-
- Usage: pyrsa-priv2pub [options]
-
- Reads a private key and outputs the corresponding public key. Both
- private and public keys use the format described in PKCS#1 v1.5
-
- Options:
- -h, --help show this help message and exit
- --in=INFILENAME Input filename. Reads from stdin if not specified
- --out=OUTFILENAME Output filename. Writes to stdout of not specified
- --inform=INFORM key format of input - default PEM
- --outform=OUTFORM key format of output - default PEM
+ openssl genrsa -out myprivatekey.pem 512
+
+To get a Python-RSA-compatible public key from OpenSSL, you need the
+private key first, then run it through the ``pyrsa-priv2pub``
+command::
+
+ pyrsa-priv2pub -i myprivatekey.pem -o mypublickey.pem
+
+Encryption and decryption is also compatible::
+
+ $ echo hello there > testfile.txt
+ $ pyrsa-encrypt -i testfile.txt -o testfile.rsa publickey.pem
+ $ openssl rsautl -in testfile.rsa -inkey privatekey.pem -decrypt
+ hello there