It’s using a combination of multicollision attacks against MD5 and sequences of groups of alternate blocks of data representing the alphabet encoded in a way compatible with the file format.
It’s basically <[a+random]/[b+random]/[c+random]…> * (length of message). The random data is crafted by the attack tool so each block has the exact same effect on the MD5 hashing algorithm as it processes each block. You need to decide how many variable blocks you need and where and their encoding in advance. You encode the blocks so the randomness isn’t visible in the final rendered file.
When you have that prepped, you compute the final hash, then at each block position you select the block representing the letter you want (and its associated random data). So then you can select letters matching the actual file hash value.
It only works against hash functions with practical multicollision attacks. Doesn’t work on SHA256 and newer hashes.
Tldr, modern hash algorithms process data in fixed size blocks. For MD5 you take 128 bits at a time.
The core function in a hash is a little scrambler function (permutation) that takes two different inputs and gives you a single output back.
So it starts with a fixed value built into the algorithm, and then scrambles the first block of the message with it. Then it takes that scrambled piece and mixes that with the next block of the message, then takes THAT scrambled piece and mixes it with the next block. And so on until the end of the message. The last scrambled piece is the hash value.
Collision attacks target that core function by figuring out how to tweak multiple messages so that their scrambler outputs “collide”, ending up equal. So you can hash two tweaked messages and get the same hash value. These tweaks usually include a bunch of random looking bits to work.
Then for a multicollision we don’t just do it for two messages. We do it for every letter in the alphabet. For a HTML document we encode something like <div hidden garbage=xyz>a</div> and repeat for every letter. Every letter gets a distinct random looking value. Then we have many documents with the same hash and one letter different. We can show you a hash and then pick which letter to present you with in the document. All of them checks out.
But then we repeat the attack. We add another whole alphabet right after the first one! Now we have <div hidden_garbage=xyz>a</div> <div hidden_garbage_2=xyz>a</div>. And because the second letter is in a different block, that works just fine! Adding a second letter don’t change the first intermediate value, and you can attack the second intermediate value for the second letter separately. So you add the whole alphabet again (with new associated calculated garbage for every letter in the second position), and now after the second letter we have a new intermediate value which is the same regardless of which letter we pick in the second position.
So now we can independently pick a random letter in the first position and in the second position too! Every combination of two letters has the same hash because of the hidden calculated garbage after each letter!
Then we just repeat the multicollision attack on the whole alphabet over and over until your document is long enough to encode your message. And that message may include the document’s own hash.
Okay first of all this message is really nicely written to explain multi collision attacks! (I knew some stuff about hashing and collision attacks before but not about multi collision and why that would be really useful here.)
However, I first thought they were looking for inputs which basically preserve a known state and then generating an alphabet with those kinds of blocks (basically have one for each symbol and up to n additional blocks to “reset” the state to the known value) because that could shrink the size of stored blocks by a lot (I’d imagine).
But now I am wondering if that’s even possible currently (even with an algorithm as “broken” as MD5 has become now)?
That’s a second pre-image attacks when you’re targeting existing state (attacking hash values of existing data by creating a second file matching it). For some reason even with MD5 that’s still infeasible - but collision attacks where you don’t have a target output value, but instead have partial target inputs which need to have the same output hash, are however practical and fast.
You can but you need to define what part of the data the signature covers (a signature can’t sign itself, so it must be excluded from the data bundle). Signed PDF files has the signature appended after the document data
Exactly. And even though there are message start and end markers it’s not quite clear at which pixel the signed image starts and ends. Also the image format that is signed is not defined.
This person was being the authorized representative of themselves. Sovcits, for a variety of reasonings, often refuse to admit that they are the legal person who is being charged. They often make a convoluted distinction between the actual person and the legal person, so they show up as the actual person to “settle the matters” of the legal person.
You can’t be an authorized representative of somebody else for a crime/infraction unless you are a lawyer anywhere I know of in the U.S. A person representing is either a lawyer or self-represented. You can’t just pick some rando as your champion to show up in your place. Judges have smacked Sovcits legally in various ways for this stunt.
The most entertaining result is them stubbornly refusing to admit that they are “Name” and the judge issuing a warrant for failing to appear because the named defendant didn’t show up to court.
Usually at that point they crack, but I’ve seen one zoom court where the judge just ends the hearing with the warrant issued.
It’s interesting how sovcits have so recently and dramatically changed.
There have always been a few people who thought they could somehow carve out their own territory in the middle of the United States, or that for some reason the laws wouldn’t apply to them. There have been jokes about them on the Simpsons and elsewhere.
But it was all individual. It wasn’t this Q-Anon like conformity, and, while always ridiculous, not quite this delusional. This new sovcit thing is different and propaganda/single large cult fueled.
Except PGP is a substring of the ‘technically correct’ term. It’s like someone saying you’re playing on your Nintendo - “Um, actually it’s a Nintendo 64.”
It’s actually quite similar. Non-fungible since only OP has the private key but easy to steal by just downloading the image (and cropping the key if you want).
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