Reposted from r/piracy, in case the subreddit gets taken down:

This could be useful for those who want to share content - legal or illegal - but don't want links to be taken down. NOTE: I don't run any of these websites, nor do I develop any of the tools mentioned. I just found them through web searches. This is based on what Phil Carmody did with DeCSS (i.e. finding a 1401-digit prime based on said software).

To encode:

1. Convert the link (or file) from ASCII to HEX by pasting (or loading) it into a HEX editor's "Decoded text" field (I use HxD for this step).
2. Copy the HEX values to clipboard.
3. Go to this page, paste the number into the "Enter a big number" field, and select "Hexadecimal" and "Decimal" from the 2 drop-down boxes directly beneath it. Hit convert.
4. Copy the resulting number to the clipboard.
5. Go to FactorDB, paste the resulting number into the text field, and hit Enter.
6. Where it says "status (?) digits number", right-click on the link under "number" and click "Copy link location" (or equivalent function).
7. Paste the link into a text document, and copy the ID (the number at the end of the link, usually 19 digits and starting with 1100000...).
8. Paste the ID wherever you want, except r/piracy.

To decode:

1. Paste the resulting ID after "http:// www dot factordb dot com/index dot php?id=", or multiply the prime factors given.
2. Go to the number converter link (given in Step 3 of the encoding process above), and repeat Step 3, but instead of converting from HEX to DEC, we're doing it the other way around.
3. Copy the resulting HEX code and paste into the HEX editor you're using. 4a. If the result is a link, copy the link and paste into your browser's address bar (best to examine the link first, in case of malware/CP).
   4b. If the result is a file (i.e. it looks like gibberish in the "Decoded text" field), save it with a name reflecting the source page's title (i.e. if it's a keygen/crack, save it as [product name]_Keygen.exe). Check it with VirusTotal if you don't trust the source website. Delete if malware or CP.

Here's an example ID, produced from "https://www.example.com/": 1100000004141947535

Make sure you put the IDs of your encoded links into a Pastebin paste or similar uploaded document with encode/decode instructions for backup/distribution purposes.

Another possibility, if the number is relatively easy to factor (usually less than 140 digits), is to copy the prime factors (i.e. "17 4567 9043 260527 118318993678213 118344575811172420048687170089") instead of the ID. You can rearrange the factors (i.e. "17 118344575811172420048687170089 9043 118318993678213 4567 260527") if you want, to reduce the chance of copyright troll detection.

I'm sure this will reduce the number of links taken down by a considerable amount. They'll likely be looking for actual links (or Base64-encoded strings), not prime factors (or 19-digit integers starting with 110000...). I think the prime factors method is more secure, as it doesn't always have the same length, unlike the DB ID method. There are plently of software tools out there for factoring numbers, of which the command-line tools YAFU and GGNFS are the easiest to set up (there are precompiled binaries available for both). If the number is too large, factoring it might not be feasible with current hardware, in which case the DB ID method is better.