SILC(1)

NAME
silc - client for SILC, a secure and flexible conferencing network

SYNOPSIS
silc [ -S file | -d | -C | -c host | -w pass | -p port | -! | -n nick | -h host | -v | -? ]

DESCRIPTION
SILC (Secure Internet Live Conferencing) is a secure conferencing network. Silc is the SILC client which is used to connect to SILC server and the SILC network. The silc client resembles IRC clients to make the using easier for new users.

Silc supports sending of practically any kind of messages in addition of normal text messages in the SILC network. This includes multimedia messages like images, video and audio stream. The session to SILC server is secured with session key, channel messages are protected with channel key and private messages with session keys. It is also possible to use private channel keys and private message keys in addition to server generated keys. It is also possible to digitally sign all messages.

Silc supports passphrase authentication and public key authentication based on digital signatures, when connecting to SILC server. Silc also supports key exchange (key agreement) between other Silc users in the SILC network to negotiate secret key material. This key material then can be used to secure for example private messages. It is also possible to exchange public keys and certificates in the SILC network between clients and servers.

The silc also supports detaching from the SILC network by closing the connection to the server but without quitting from the network. Next time the silc connects to the server it resumes the session in the SILC network. During the detaching the user remains in the network and other users may query the user information and see that user is in network but currently detached. Messages sent to user while being detached are dropped by the server. When resuming is over the user has automatically same nickname than before detaching and remains on all channels, and it seems like user never left the network.

The silc also supports creation of friends list, which is kind of a buddy list familiar from IM (Instant Messaging) clients. By using the WHOIS SILC command with -details option it is possible to fetch the user’s information such as their public keys and certificates, business card, pictures, and other information and save them to the friends list. The friends list is located at ~/.silc/friends/ directory.

The SILC public key and private key pair is used to authenticate the user to the SILC server when connecting a server. This key pair is created automatically when the silc is run for the first time. It can also be created with -C option.

When connecting for the first time to SILC server, user will be asked to accept the server’s public key. When key is accepted the silc saves the public key for future into ~/.silc/serverkeys/ directory. The next time user connects to same server the public key is verified against the saved public key. The purpose of this public key saving is to avoid man-in-the-middle attacks which could be possible if the key would have to be verified every time user connects to the server.

OPTIONS
-c host Connect to given host

-p port Connect to port

-C Create new public key pair

-P Change the passphrase of the private key file

-S keyfile Display the contents of given SILC public key from file

-n nick Specify what nick to use

-h host Give host as your hostname

-w pass Use pass as password for connection

-d string Enable debugging

-v Display client version

-! Do not autoconnect

-? Display client help message

LONG OPTIONS

--connect=SERVER Same as -c.

--port=PORT Same as -p.

--home=PATH Client home dir (~/.silc).

--config=PATH Configuration file location (~/.silc/silc.conf).

--list-ciphers List supported ciphers.

--list-hash-funcs List supported hash functions.

--list-hmacs List supported HMACs.

--list-pkcs List supported PKCSs.

--create-key-pair Same as -C.

--passphrase-change Same as -P.

--nick=NICK Same as -n.

--hostname=HOST Same as -h.

--password=PASS Same as -w.

--debug=STRING Same as -d, limit to messages *STRING*.

--dummy Use dummy terminal mode.

--version Same as -v.

--noconnect Same as -!.

--help Same as -?.

--usage Display very brief usage summary.

KEY GENERATION
When generating key pair(s) for silc (-C), the following extra switches apply:

--pkcs=PKCS Set the public key algorithm of key pair. For example rsa.

--bits=VALUE Set the length of public key pair, in bits.

CONFIGURATION FILE
The silc configuration file is ~/.silc/silc.conf and can be used to configure the behaviour of the client. The configuration file format is equivalent to Irssi IRC client’s configuration file. See the documentation for the configuration file at http://irssi.org.

There are a few silc configuration settings in silc.conf which can be configured in settings section under "server" block. They can be set also with the /SET command in the silc client.

crypto_default_cipher
    The default cipher to use to secure the session to the server. Values can be for example aes-256-cbc, aes-192-cbc, aes-128-cbc, twofish-256-cbc, twofish-192-cbc, twofish-128-cbc.

crypto_default_hash
    The default hash function to use in session with the server. Values can be sha1 or md5.

crypto_default_hmac
    The default HMAC to be use in session with the server. Value can be hmac-sha1-96, hmac-md5-96, hmac-sha1 or hmac-md5.

FILES
~/.silc/silc.conf
    Client’s configuration file

~/.silc/public_key.pub
    The SILC public key of the user

~/.silc/private_key.pub
    The SILC private key of the user

~/.silc/clientkeys/
    The directory holding the public keys of other users the user has accepted and trusted in the SILC network. The public keys can be received with GETKEY SILC command or during key agreement between two users.

~/.silc/serverkeys/
    The directory holding the public keys of servers the user has accepted and trusted when connecting to a server.

~/.silc/friends/
    The directory holding the information of friends that user has. User can create a friend list with WHOIS -details SILC command. This directory holds the friends’ public keys, business cards, pictures, and other information.

SEE ALSO
silcd(8) silcd.conf(5)

NETWORK RESOURCES
Homepage: http://silcnet.org

SILC Client is based on Irssi IRC client: http://irssi.org

User’s guide: http://silcnet.org/docs/

AUTHOR
SILC is designed and written by Pekka Riikonen <priikone@iki.fi> and rest of the SILC Project.

This manpage was written by Mika ’Bostik’ Boström <bostik@lut.fi>

See CREDITS for full list of contributors.