5 ms·

Cobbling together existing primitives counts as "rolling your own crypto". They did it in a trivially stupid way, but it is still a botched attempt at cryptogr

• Someone1234 11y ago
  > Cobbling together existing primitives counts as "rolling your own crypto". MD5() isn't a primitive, it is an entire implementation. As I said, if they didn't do maths they didn't do encryption. You're conflating authentication with encryption, which aren't the same thing at all (just like an engine and a car aren't the same thing, or a heart and a human). Encryption (and or hashing) is an important part of authentication, but the term "rolling your own encryption" clearly relates to the encryption-part of the authentication routine. People regularly roll their own authentication routines (even if that within its own right is a bad plan). I am in no way defending that code. It is garbage. But people in this thread have clearly misunderstand the warning against "rolling your own encryption." Or don't know what encryption is.
  • frankzinger 11y ago
    > MD5() isn't a primitive, it is an entire > implementation. No, it's a primitive. From https://en.wikipedia.org/wiki/Cryptographic_primitive https://en.wikipedia.org/wiki/Cryptographic_primitive: Commonly used primitives One-way hash function, sometimes also called as one-way compression function—compute a reduced hash value for a message (e.g., SHA-256) Furthermore: Cryptographic primitives are one of the building block of every crypto system, e.g., TLS, SSL, SSH, etc. ... Combining cryptographic primitives to make a security protocol is itself an entire specialization. Most exploitable errors (i.e., insecurities in crypto systems) are due not to design errors in the primitives (assuming always that they were chosen with care), but to the way they are used, i.e. bad protocol design and buggy or not careful enough implementation. This last bit is usually what is meant by "don't roll your own crypto". Granted, the parent said "encryption", but he meant "crypto", and I thought that was quite clear from the context.
    • pygy_ 11y ago
      > This last bit is usually what is meant by "don't roll your own crypto". Granted, the parent said "encryption", but he meant "crypto", and I thought that was quite clear from the context. That's how I read it — and therefore misquoted it — as well.
    • Someone1234 11y ago
      It is in the context of building a larger cryptographic protocol. But they aren't building a cryptographic protocol in this case, so none of that applies here at all, even a tiny bit. In this case hashing functions are being used stand alone (both bcrypt and MD5), and therefore they're not cryptographic primitives. The only time they become cryptographic primitives is when they're used as such, in a cryptographic protocol, which it isn't here. You may have read that Wikipedia entry but I don't think you understood it, it says this quite clearly. To be honest it is just flabbergasting we're even having this discussion. "Encryption" has a very specific meaning that is hundreds of years old, "crypto" is just a shorthand way of writing encryption or cryptographic, and neither term is a synonym for authentication. I cannot tell if this confusion originates from people not understanding what the words "encryption" or "cryptographic" mean, or from them not understanding the difference between authentication as a broader topic and encryption/hashing as a singular component within it. If people want to create the mantra of "don't roll your own authentication," then more power to you. But none of this has anything to do with "don't roll your own crypto." They categorically did not at any point roll any crypto, encryption, cryptographic protocols, or anything else related. Just custom authentication. As I have said multiple times in this thread: "No maths used == no attempt at rolling their own crypto." It is as simple as that, so unless someone can point me to their bespoke implementation of crypto (i.e. maths) then what you're arguing doesn't make sense. To use an analogy: - Famous mantra is: "Never roll your own car engine." - Article is posted where someone built a custom car using an off-the-shelf engine (even if an old and dangerous one (i.e. MD5)) and it crashes. - Someone replies: "This is why you NEVER roll your own car engine." - I reply: "They didn't roll their own car engine, it was a standard off-the-shelf one!" - Someone replies: "The term 'car engine' (as in "Never roll your own car engine") now refers to the ENTIRE CAR, not just the engine." - I reply: "No the engine is a specific component in the car." (i.e. MD5 is a specific off-the-shelf component in an authentication scheme). - Someone replies: "The term 'car engine' now means 'car.'" (i.e. the term "crypto" now refers to the entire authentication process for some reason). As I said I feel like slamming my head on the table. I don't know another way of explaining this. The fact you think that Wikipedia article has any relation to this topic at all means you're even further from understanding this than I thought. Do you really think an authentication scheme is a cryptographic protocol? Is AES an authentication scheme? Is Kerberos a cryptographic protocol? No, and no. Kerberos USES encryption and AES is used IN authentication schemes, but they're just components in both cases.
  • fryguy 11y ago
    MD5 is a primative. Many algorithms specify a hash/compression function (which MD5 is) or a permutation (which AES is) in how they work. Message authentication (HMAC) can use any compression function, key derivation can use any compression function, and so on. Even stream ciphers can use MD5. People implementing things that use crypto should only be using functions that are "Authenticated Encryption" which specify the full suite like AES-GCM (permutation function: AES, in Galios/Counter Mode), or "Key Derivation Function" (PBKDF2-HMAC-SHA2 or Argon2d-Blake2b). What they've done at AM is implement their own key derivation function using the MD5 primative and concatenation.