Stunnel

Nitrokey 3	Nitrokey Passkey	Nitrokey FIDO2	Nitrokey U2F	Nitrokey HSM 2	Nitrokey Pro 2	Nitrokey Start	Nitrokey Storage 2
✓	⨯	⨯	⨯	✓	✓	✓	✓

Stunnel works as an SSL encryption wrapper between remote client and local (inetd-startable) or remote server. It can be used to add SSL functionality to commonly used inetd daemons like POP2, POP3, and IMAP servers without any changes in the programs’ code.

Stunnel is able to load OpenSC PKCS#11 engine using this configuration:

engine=dynamic
engineCtrl=SO_PATH:/usr/lib/opensc/engine_pkcs11.so
engineCtrl=ID:pkcs11
engineCtrl=LIST_ADD:1
engineCtrl=LOAD
engineCtrl=MODULE_PATH:/usr/lib/pkcs11/opensc-pkcs11.so
engineCtrl=INIT

[service]
engineNum=1
key=id_45