File: gnupg.info,  Node: Agent Protocol,  Prev: Agent Examples,  Up: Invoking GPG-AGENT

2.6 Agent's Assuan Protocol
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Note: this section does only document the protocol, which is used by
GnuPG components; it does not deal with the ssh-agent protocol.  To see
the full specification of each command, use

       gpg-connect-agent 'help COMMAND' /bye

or just 'help' to list all available commands.

The 'gpg-agent' daemon is started on demand by the GnuPG components.

   To identify a key we use a thing called keygrip which is the SHA-1
hash of an canonical encoded S-Expression of the public key as used in
Libgcrypt.  For the purpose of this interface the keygrip is given as a
hex string.  The advantage of using this and not the hash of a
certificate is that it will be possible to use the same keypair for
different protocols, thereby saving space on the token used to keep the
secret keys.

   The 'gpg-agent' may send status messages during a command or when
returning from a command to inform a client about the progress or result
of an operation.  For example, the INQUIRE_MAXLEN status message may be
sent during a server inquire to inform the client of the maximum usable
length of the inquired data (which should not be exceeded).

* Menu:

* Agent PKDECRYPT::       Decrypting a session key
* Agent PKSIGN::          Signing a Hash
* Agent GENKEY::          Generating a Key
* Agent IMPORT::          Importing a Secret Key
* Agent EXPORT::          Exporting a Secret Key
* Agent ISTRUSTED::       Importing a Root Certificate
* Agent GET_PASSPHRASE::  Ask for a passphrase
* Agent CLEAR_PASSPHRASE:: Expire a cached passphrase
* Agent PRESET_PASSPHRASE:: Set a passphrase for a keygrip
* Agent GET_CONFIRMATION:: Ask for confirmation
* Agent HAVEKEY::         Check whether a key is available
* Agent LEARN::           Register a smartcard
* Agent PASSWD::          Change a Passphrase
* Agent UPDATESTARTUPTTY:: Change the Standard Display
* Agent GETEVENTCOUNTER:: Get the Event Counters
* Agent GETINFO::         Return information about the process
* Agent OPTION::          Set options for the session