Smartcard Authentication - Secure & Easy

Secure Shell with Smart Card Authentication

PuTTY, the free SSH implementation from Simon Tatham, does support public key authentication but lacks support for smart cards. An enhancement request for PuTTY asking for smart card support within the original PuTTY package has been on the PuTTY wishlist for a very long time.

PuTTY.exe may read a private key from a file or may talk to an SSH authentication agent, which will do all cryptographic operation on behalf of the actual putty.exe. The PuTTY-Package contains such an agent, i.e. pageant.exe, but this agent can also read private keys from password protected files only.

In the download area of this website you will find a replacement for pagent.exe that does support smart cards.

This smart card enabled pageant.exe has the following additional features:

• As a security product PuTTY tries to avoid dependencies on external libraries. So does the smart card enabled version of pageant.exe. It does not use any kind of smart card middleware (neither OpenSC nor PKCS#11 nor CSP) but talks directly to your smart card via the PC/SC driver of your smart card reader (WinSCard-API).
• Secure PIN Entry is supported for smart card readers with pinpad (disabled for non-registered public keys).
• Public keys from your smart card will be inserted/removed automatically into pageants keylist on smart card insertion/removal.
• If your smart card contains multiple private keys all of them will be inserted into pageants keylist and may be used simultaneously.
• If you have mutiple cardreaders attached to your PC all of them will be scanned for smart cards and may be used simultaneously.
• As on option pageant may store the PIN of your smart card in memory until you shutdown the agent.
• Support for CryptoFlex smart cards.
• Support for almost all TCOS based smart cards, in particular NetKey E4 cards from TeleSec GmbH and all TCOS based german signature cards.
• Support for some CardOS based cards, in particular the D-Trust 2048bit card.
• Support for german Health Professional Cards.
• Support for Aladdin eToken PRO (32K and 64K).
• Support for Sicrypt smart cards.
• Support for the OpenPGP (version 1+2) smart card and the OpenPGP CryptoStick.
• Support for 2048bit RSA-keys.
• Creates key-descriptions for all of your smart cards public keys which may be inserted into your authorized_keys file via Cut&Paste. Just insert your smart card with your control-key pressed.
• Supports all applications that implement the SSH authentication agent protocol. In particular pageant.exe will work with WinSCP and the Filezilla-Client.

If your smart card does not work then the reason is most likely that you are the first one to try this particular card. If OpenSC supports your card then it will be relatively easy to add support for your card to pageant.exe as well. You only have to email OpenSC debug-output with highest verbosity level to support@smartcard-auth.de and must be willing to do some tests. In return for your testing activities I will register your public keys for free.

If your smart card does neither work with pageant.exe nor OpenSC then a test card and documentation is most likely needed to add support for such a card. Please send informtion about your smart card to support@smartcard-auth.de if you own such a card.

Installation

Installation is easy:

• Install PuTTY with putty-0.60-installer.exe from the PuTTY download page.
• PuTTY will install itself into one directory (normally C:\Program Files\PuTTY). There you will find pageant.exe, the SSH authentication agent. Replace this executable with pageant.exe from the download area.
• Using PuTTY and/or the SSH authentication agent is described in the PuTTY-documentation. Besides the possibility to use smartcards there is only one difference. If you insert your smartcard with your control-key pressed pageant.exe will write information about all your public keys into a textfile.

Registering your Public Key

If you use pageant.exe with a non-registered public key then Secure PIN entry will be disabled and pageant.exe will connect to a destination only after a short delay.

You may evaluate pageant.exe with a non-registered public key for at most 30 days. It will be functional for a longer time though.

Please do NOT register OpenPGP cards or the OpenPGP CryptoStick. In order to support this free project owner of such cards/sticks may use pageant.exe as long as they like. Secure PIN entry is enabled for OpenPGP cards and SSH-connections start without a delay. The About-dialog still mentions the 30 day trial period. Please ignore this if you are using an OpenPGP card/stick.

You cannot register the software but must register your public key instead. This has the following consequences:

• Once a key was registered you may use it with as many current (or future) versions of pageant.exe as you like.
• If you are able to store your private key into multiple smart cards you will only need one licence to use these cards with pageant.exe. Of course creating multiple smart cards containig the same private key is against the idea of using a smart card as a unique two factor authentification token. This might be a reasonable way to replace a lost or broken smart card. I recommend not to do so.
• If your private key is stored within your smart card only, then there is no way to recover your private key if you loose your smart card or block your PIN permanently. You will need a new card with a new private key then. And you must also reregister your new public key. There will be no refund for registration fees of lost private keys.