7. Compatibility with standards

Python-RSA implements encryption and signatures according to PKCS#1 version 1.5. This makes it compatible with the OpenSSL RSA module.

Keys are stored in PEM or DER format according to PKCS#1 v1.5. Private keys are compatible with OpenSSL. However, OpenSSL uses X.509 for its public keys, which are not supported.


PKCS#1 v1.5 with at least 8 bytes of random padding


PKCS#1 v1.5 using the following hash methods: MD5, SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA3-256, SHA3-384, SHA3-512

Private keys:

PKCS#1 v1.5 in PEM and DER format, ASN.1 type RSAPrivateKey

Public keys:

PKCS#1 v1.5 in PEM and DER format, ASN.1 type RSAPublicKey

VARBLOCK encryption:

Deprecated in Python-RSA 3.4 and removed from Python-RSA 4.0. Was Python-RSA only, not compatible with any other known application.

7.1. Interoperability with OpenSSL

You can create a 512-bit RSA key in OpenSSL as follows:

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

7.2. Interoperability with PKCS#8

The standard PKCS#8 is widely used, and more complex than the PKCS#1 v1.5 supported by Python-RSA. In order to extract a key from the PKCS#8 format you need an external tool such as OpenSSL:

openssl rsa -in privatekey-pkcs8.pem -out privatekey.pem

You can then extract the corresponding public key as described above.