# $EPIC: xform.txt,v 1.10 2012/07/04 06:30:23 jnelson Exp $
$xform(“<encodings>” “<metas>” <text>)
The $xform() function transforms the <text> into some other form. There are three types of transformations:
|Encryption||Convert plain text into encrypted ciphertext|
|Encoding||Convert any kind of data into a valid C string|
|Hashing||Convert any kind of data into a message digest|
|Transcoding||Convert a string between different character sets|
Encryption works by taking your plain text and a password key and flipping some of the bits, which gives you output that looks like random bytes. The only way to recover the original text is to have the password key.
Because encryption usually gives you binary data, which can't be used directly in the client, you have to encode it into a usable format.
Both encryption and encoding are symmetric – they are fully reversable, and all of the information in the input data is present in the output data, but in some different way.
Hashing is different. Hashing is a form of lossy compression that takes any input data and removes all but a little bit of the information. Because is lossy compression, it is irreversable. Unlike encryption, there is no way to recover the original text from a hash.
The xform function supports the following encryptions that all take one required argument.
|SED||Simple Encrypted Data||Password|
|AESSHA||AES256-CBC with SHA256 digest of password||Password|
|DEF||Default encryption (not supported yet!)||Password|
The xform function supports the following encodings that do not take arguments.
|URL||Perform RFC3986 transformation (“URL encoding”)|
|ENC||Perform Base-16 transformation|
|B64||Perform RFC1421 transformation (“Base 64”)|
|FISH64||Perform l64a transformation (“FiSH” ascii armoring)|
|CTCP||Perform CTCP transformation|
|NONE||No changes (just copies the string)|
|ALL||Return all supported transformations (ignores the text)|
The xform function supports the following transformations that take one required argument.
|ICONV||Iconv charset transformation||FROM/TO (see below)|
The xform function supports the folowing digests:
|SHA256||SHA256 Message Digest|
$xform("<transformations>" "meta" "meta" text)
You can string together multiple transformations. Any transformation that requires a meta value (ie, a cipherkey) should be supplied after the transformations in the correct order. After this should be the plain text. To apply a transformation, prefix its name with a plus sign (“+”) and to remove a transformation, prefix its name with a minus sign (“-”). For example, +URL means url encode, and -URL means url decode.
Normally functions do not accept dwords as arguments, but xform does. If you want to do multiple transformations at once, you must separate them by spaces and surround the whole thing in double quotes. If the meta values (ie, passwords for encryption) contain spaces, you must surround the meta value with double quotes.
For the ICONV transformation, the “meta” value is a word that contains the old encoding and the new encoding separated by a slash (“/”). There is no guaranteed list of encodings that you can use, because it depends on your system's iconv(3) facility.
Example: To convert a string from iso-8859-1 to utf8,
$xform(+ICONV "iso-8859-1/utf8" ...)
|If you want to:||Then you should…|
|URL-encode a string||$xform(+URL this is a string)|
|URL-decode a string||$xform(-URL this%20is%20a%20string)|
|SED-cipher a string||$xform(+SED password this is a string)|
|SED-decipher a string||$xform(-sed password <whatever>)|
|Iconv transform a string from utf-8 to iso-8859-1||$xform(ICONV “utf-8/iso-8859-1” $utf8string)|
More practical examples:
@fd = open(file.txt R) @data = read($fd 1024) @cipher = xform("-CTCP +SED +URL" password $data) @close($fd) msg someone $cipher
Why does this work?
We can send this to someone else, and they can put it in $cipher…
@newfd = open(newfile.txt W) @newdata = xform("-URL -SED +CTCP" password $cipher) @writeb($newfd $newdata) @close($newfd)
We did the reverse of the above: