Dear Yoann, thank you very much for this simple solution!

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I have setup smartcard logon on OS X Yosemite and now each time I login using smartcard I see pop up dialogue "messages agent wants to use the login keychain. Enter the password". I understand that the Login keychain is protected by user's password and usually is is opening by OS X with the password, but now OS X has no my password, it has only PIN for my smart card. Is there any solution not to use password to unlock Login keychain?

Yes, you can replace your keychain password by your PIN code. It’s not a good practice in terms of keychain protection but it will automatically unlock it at the logon time.

Cheers, Yoann

Best regards, Vadim