A trip (トリップ, torippu), or tripcode, is an optional string of characters used for identification on some bulletin boards. It was first introduced to 2channel as the “one-person capcode” (一人用キャップ, hitori-yō kyappu) in August 2001 to avoiding giving capcodes to absolutely everyone.

In anonymous communities, trip usage is considered to be bad manners when it's only used to stand out. Those who can't read the atmosphere usually get berated and it's best to silently return to anonymity. While rare, extensive inappropriate use has led to doxing.

To use a tripcode, one must input a half-width number sign (#) in the name field and put a random character string or 'password' after it. For the character string, the first eight half-width characters (#1234567890) or first four full-width characters (#あいうえお) matter, while everything after is irrelevant. You can mix half- and full-width characters (#abcあいdうefえ), but everything after 8 bytes is ignored.

When making a post, the trip will typically show up where you find the default name after a trip key. On most Japanese boards, a trip key is a black diamond (◆) which changes into a white diamond (◇) if you try to spoof it. On most foreign boards, the trip key is an exclamation point (!). Based on the board settings, the trip key can be changed or trip usage may be disabled altogether.

Historically, the trip generation method consists of converting the given input into Shift_JIS, adding salt as shown below, calling Perl's crypt function, and spitting out the last few characters of the encrypted string with the trip key as the output. Originally, the last eight characters of the encrypted string is what was used in the output until it was expanded to the last ten characters on October 3, 2002.

$tripkey = "#istrip";  # Tripcode String (with #)
$tripkey = substr $tripkey, 1;
$salt = substr $tripkey . "H.", 1, 2;
$salt =~ s/[^\.-z]/\./g;
$salt =~ tr/:;<=>?@[\\]^_`/A-Ga-f/;
$trip = crypt $tripkey, $salt;
$trip = substr $trip, -10;
$trip = "◆" . $trip;
print $trip, "\n";

$salt = strtr(preg_replace("/[^\.-z]/",".",substr($trip."H.",1,2)),":;<=>?@[\\]^_`","ABCDEFGabcdef");
$trip = substr(crypt($trip, $salt),-10);
$name.=" <span class=\"postertrip\">!".$trip;

def mk(pw):
    pw = pw[:8]                   # get the first 8 chars
    salt = (pw + "H.")[1:3]       # make the salt 
    trip = crypt.crypt(pw, salt)  # apply unix crypt()
    return trip[-10:]             # grab the last 10 chars of hash

This is the extended trip generation method that appears to be used on some 2channel boards. The following encryption method is from June 2009, so it's possible that the code may have changed since then.

if (length $handle_pass >= 12)
{
    my $mark = substr($handle_pass, 0, 1);
    if ($mark eq '#' || $mark eq '$')
    {
        if ($handle_pass =~ m|^#([[:xdigit:]]{16})([./0-9A-Za-z]{0,2})$|)
        {
            $GB->{TRIPSTRING} = substr(crypt(pack('H*', $1), "$2.."), -10);
        }
        else
        {
            # For Future Expansion
            $GB->{TRIPSTRING} = '???';
        }
    }
    else
    {
        use Digest::SHA1 qw(sha1_base64);
        $GB->{TRIPSTRING} = substr(sha1_base64($handle_pass), 0, 12);
        $GB->{TRIPSTRING} =~ tr/+/./;
    }
}
else
{
    # Traditional Method
}

On 4chan, using a second half-width number sign will generate a “secure tripcode” using the following code according to a 2010 leak.²⁾ It's presumed that the salt or method has been changed since then.

if ($sectrip != "") {
    $salt = "LOLLOLOLOLOLOLOLOLOLOLOLOLOLOLOL"; #this is ONLY used if the host doesn't have openssl
                                            #I don't know a better way to get random data
if (file_exists(SALTFILE)) { #already generated a key
    $salt = file_get_contents(SALTFILE);
} else {
    system("openssl rand 448 > '".SALTFILE."'",$err);
    if ($err === 0) {
        chmod(SALTFILE,0400);
        $salt = file_get_contents(SALTFILE);
    }
}
    $sha = base64_encode(pack("H*",sha1($sectrip.$salt)));
    $sha = substr($sha,0,11);
        if($trip=="") $name.=" <span class=\"postertrip\">";
        $name.="!!".$sha;
}

A leaked trip (トリ漏れ, tori more), or public trip (公開トリップ, kōkai torippu), refer to cracked tripcodes whose password have either been cracked using brute force or made public. There are 2⁵⁸ (≈ 2.88×10¹⁷) possible trip combinations. It was once speculated that regular trips take 15,000 to 30,000 years to crack, but as technology evolves, regular tripcodes can be cracked faster and possibly within hours.

These tools were originally made with the intent to leak trips, but they can also be used to help people find a unique trip that they could use. The tool works by inserting a combination of letters, numbers, and symbols for the tool to look for. Depending on the length, it will usually return results in a couple of minutes, or it could probably take 15,000 years to find the exact 10-character match.

• Project: NANIYA / “MTY” (“2008-12-22”).
  This is one of the more recent tools. Some people claim that it only works with modern ATI cards.
• Meriken's Tripcode Engine
  Recommended in the past. The developer sorta vanished after the 2channel split.
• MTY_CL
  For some reason, this was the second recommended tool in the past, though I can't remember why.
• Tripcode Explorer (2009-09-26)
  This was, allegedly, an English translation of a much older tool used on 2channel.

• Here's a quick rundown on what trip users are called in Japanese and what the primary types are:
  • “Kotehan” (コテハン) means “fixed user name” (固定ハンドルネーム, kotei handoru nēmu).
  • “Sutehan” (捨てハン) means “disposable user name” (捨てハンドルネーム, sute handoru nēmu).
  • “Kusokote” (糞コテ) is an insult that roughly has similar connotations to “shitty tripfag”.
• The word, “tripcode”, may come from World2ch's FAQ where it was called a “trip code”.³⁾ It seems like this translation was used to allude to trips being similar to passwords or passcodes.
• Back in 4chan's early days, “0037” introduced Poole to trips who would compare them to registration⁴⁾ and encourage use of them with a “Protect your identity! Use tripcodes!” bullet point.

• Capcode

• Trip (Electronic Bulletin Board) on Japanese Wikipedia
• Trip on Niconico Encyclopedia
• Tripcode Tester - Japanese tool for testing multiple tripcodes at once.