# Siemens CardOS M4

Siemens CardOS M4 smart card should work fine with OpenSC.

Supported smart cards are the Aladdin eToken PRO and the Eutron ITSEC-I USB tokens.

Currently only the Aladdin eToken PRO is tested often (a usb crypto dongle that contains a card with this operating system). It works fine, so all other smart cards with the same card operating system should work fine, too.

Siemens CardOS M4 does not allow a key to be used for signing and decryption. OpenSC has a workaround for this restriction, you can generate or store a private key with the "--split-key" flag which will store the key twice, with different usage options, but hide this detail.

Some documentation is available from Aladdin for their eToken PRO, but for an in-depth documentation you need the Siemens card manual, which requires signing an NDA.

The versions of CardOS M4 are: M4.0, M4.01, M4.2, M4.3, M4.3b, M4.2b in this order. Yes, M4.2b is the latest and greatest and later than M4.3 and M4.3B.

Also note that M4.0 needs special "packages" (i.e. signed firmware addons by siemens) installed to work properly. Best not to use that ancient version if you can.