5 ms·

> Or... you can have a more nuanced viewpoint The nuanced viewpoint is never implement your own cryptography. > Its so stupid simple I don't think that even a

> Or... you can have a more nuanced viewpoint The nuanced viewpoint is never implement your own cryptography. > Its so stupid simple I don't think that even a novice would make a critical error. Ask Microsoft about that one: https://learn.microsoft.com/en-us/security-updates/securitybulletins/2010/ms10-070 https://learn.microsoft.com/en-us/security-updates/securityb...

dragontamer 4y ago
That's a Padding Oracle vulnerability, not a CBC error.
- password11 4y ago
  Padding is an important part of CBC.
  - dragontamer 4y ago
    [flagged]
    - tptacek 4y ago
      No, to all of this.
    - deleted 4y ago
      [deleted]
    - bawolff 4y ago
      By that metric all security vulnerabilities can be explained away as a fault in a different part of the system.
    - IncRnd 4y ago
      > Furthermore, padding oracles are completely irrelevant to data at rest, like as described in this topics use case. So it really is a bit of a non sequitur too. That's not true and extremely dangerous to say. In an offline, black-box scenario no server is needed for a padding-oracle. You are thinking of a side-channel oracle. A padding-oracle attack can absolutely be feasible in many cases.
      - dragontamer 4y ago
        I appreciate your efforts at actually elevating this discussion. Yes, I said something too general when I really was just trying to describe _this_ particular HTML-page encryption implementation. You're right that its possible that an offline decryption algorithm could in fact be a padding oracle under the right scenario. But I still posit it probably doesn't apply to this static-HTML page generator.
- tptacek 4y ago
  It's a CBC padding oracle, intrinsic to the operation of CBC --- if you PKCS7-pad some other mode, you do not get the same attack --- the single best-known cryptographic vulnerability on the Internet, and the parent commenter took the time to give you the most famous instance of it. For the record: that's also not the only CBC vulnerability.
- l33t233372 4y ago
  The padding is a key part of using a block cipher in CBC mode. I’m not sure why you’re ferociously defending the practice of implementing your own cryptography. It’s well known that this is a horrible idea for good reason.

dragontamer 4y ago

That's a Padding Oracle vulnerability, not a CBC error.

password11 4y ago
Padding is an important part of CBC.
- dragontamer 4y ago
  [flagged]
  - tptacek 4y ago
    No, to all of this.
  - deleted 4y ago
    [deleted]
  - bawolff 4y ago
    By that metric all security vulnerabilities can be explained away as a fault in a different part of the system.
  - IncRnd 4y ago
    > Furthermore, padding oracles are completely irrelevant to data at rest, like as described in this topics use case. So it really is a bit of a non sequitur too. That's not true and extremely dangerous to say. In an offline, black-box scenario no server is needed for a padding-oracle. You are thinking of a side-channel oracle. A padding-oracle attack can absolutely be feasible in many cases.
    - dragontamer 4y ago
      I appreciate your efforts at actually elevating this discussion. Yes, I said something too general when I really was just trying to describe _this_ particular HTML-page encryption implementation. You're right that its possible that an offline decryption algorithm could in fact be a padding oracle under the right scenario. But I still posit it probably doesn't apply to this static-HTML page generator.
tptacek 4y ago
It's a CBC padding oracle, intrinsic to the operation of CBC --- if you PKCS7-pad some other mode, you do not get the same attack --- the single best-known cryptographic vulnerability on the Internet, and the parent commenter took the time to give you the most famous instance of it. For the record: that's also not the only CBC vulnerability.
l33t233372 4y ago
The padding is a key part of using a block cipher in CBC mode. I’m not sure why you’re ferociously defending the practice of implementing your own cryptography. It’s well known that this is a horrible idea for good reason.