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Diffie-Hellman also isn't secure against determined and active attackers (with power on the network). What you say about cryptology is utter nonsense. > Your g

by DCKing 12y ago

Diffie-Hellman also isn't secure against determined and active attackers (with power on the network). What you say about cryptology is utter nonsense. > Your goal isn't crypto, but stopping casual and passive eavesdroppers. So you might as well use DES, or RC2. The algorithm doesn't matter any more. Nonsense, it's not obfuscation. If it was obfuscation, people logging the sent data would have a reasonable chance of decrypting it. If you use JavaScript to AES encrypt things (with a good password), passive eavesdroppers cannot decrypt it later without breaking AES.

valarauca1 12y ago
The weakness of Diffie-Hellman is authentication not the algorithm itself. >Nonsense, it's not obfuscation. The issue with in browser JS you seem to be completely missing is if you can't trust the network to deliver your message. How can you trust it to deliver your crypto unchanged, un-tampered, etc? The answer is you can't. If you create a system where you can, you render your crypto unnecessary.
- DCKing 12y ago
  1. The weakness of plain Diffie-Hellman is that the data you receive (the other part of the key exchange) can be from someone you can't trust. You shouldn't use plain Diffie-Hellman if your attack model includes active attackers on the network. The weakness of JS crypto is that the data you receive (the JS crypto library) can be from someone you can't trust. You shouldn't use JS crypto if your attack model includes active attackers on the network. See what I did there? 2. Under the attack model of the passive eavesdropper, the assumption is that the crypto works because the passive eavesdropper does not tamper with JavaScript. Was this not clear from my previous posts?
  - valarauca1 12y ago
    >[...]can be from someone you can't trust. So authentication? We are talking about Authentication right? Because I said that. The weakness of DHE is that you can't authenticate who are you are talking too. >You shouldn't use JS crypto if your attack model includes active attackers on the network. A crypto model has to include every possible attack vector. Crypto isn't something that happens in a vacuum. You assume the worst always. If you ever say, "No, nobody would go that far" you aren't doing crypto, your doing obfuscation. Once a message leaves your hand, everything that can go wrong, will go wrong. In crypto research people suggested moving away from SHA-1 because an attack was found, not because it was remotely possible but because it logically and mathematically existed. Crypto is about numbers and logics, not models and cost expense analysis, and what an attacker could do. Obfuscation is a game of frustration where you create a bar, and keep raising it. Your system is fundamentally broken, but you count on people getting frustrated, or bored. Before they break it. Its game of wits. :.:.: The system you're talking about isn't crypto. Its obfuscation. Your counting on somebody not moving beyond A,B, and C. Getting frustrated and giving up. Crypto doesn't do that.
    - DCKing 12y ago
      The weakness of JS Crypto is that you cannot authenticate the source of your crypto library so you cannot make sure it works properly. The problems are equivalent. All your ranting against what I'm saying is also directly applicable to plain Diffie-Hellman. Both simply are not secure under the active attacker model. That does not disqualify plain Diffie-Hellman from having some use (although not under most attack models), and that does not disqualify JS crypto from having some use (although not under most attack models). I'm going to respectfully decline discussing what attack models are and their use in security protocols on HN, as you unfortunately appear to not understand what I mean (which is probably my fault) or what attack models are used for in security research. You also appear to be confusing security research and cryptography research. You can mail me if you want to discuss this further.
      - valarauca1 12y ago
        >The weakness of JS Crypto is that you cannot authenticate the source of your crypto library so you cannot make sure it works properly One of many, this isn't the only issue. Even if you authenticate the host what prevents tampering via MitM attacks? > All your ranting against what I'm saying is also directly applicable to plain Diffie-Hellman yes and no. Standard white paper Diffie-Hellman yes. But implementations can fix that. As you point out. >That does not disqualify plain Diffie-Hellman from having some use except >and that does not disqualify JS crypto from having some use Wrong. Because you keep dodging my main point. Anything that solves the problem of: 1) Is who your talking to the right person (authentication)? 2) Is your code arriving unchanged (authentication + encryption)? The two main issues with JS crypto. Solves what ever problem your trying to solve with JS crypto. And any solution that allows you create secure JS client side crypto, fundamentally makes it obsolete. That's the problem I'm going on about.
        DCKing 12y ago
        > yes and no. Standard white paper Diffie-Hellman yes. But implementations can fix that. As you point out. Well, there we have it. I happen to have worked on a project where plain Diffie-Hellman was used not long ago. The active attacker model was genuinely not a threat/solved by other methods in this particular context, and simple confidentiality provided by a plain Diffie-Hellman key exchange was enough. As another example, plain Diffie-Hellman is also used in SSH sessions without predistributed keys [1]. Clearly, the presence of active attackers is not always a problem in the real world! If that is the case, then there also exist legitimate uses for JS crypto [2]. As a sidenote nitpick, no implementation of plain Diffie-Hellman can fix the authentication issue. There are instead variations built upon plain Diffie-Hellman (notably authenticated Diffie-Hellman) that solve the authentication issue. But these protocols are not the same as plain Diffie-Hellman. [1] RFC 4253, section 8 [2] I feel that I should stress again that although this is true for these particular use cases, JS crypto should not be trusted in general.
- gnur 12y ago
  Sometimes you don't need the data to be decrypted on the host. Your crypte is still useful if the host doesn't want to decrypt anything. Javascript crypto as an alternative to SSL makes no sence, an implementation in which the server never gets the plaintext is currently only possible with client side javascript crypto.
  - danielweber 12y ago
    I agree that any discussion of using JavaScript-crypto instead of SSL is nuts and likely a strawman complaint. But just because it's "the best we can do," that doesn't mean it's a good idea. EDIT 1 minute before I made this comment 'tptacek said the fallacy better elsewhere on this page "we really need browser crypto to work, therefore it works"."
  - marcosdumay 12y ago
    Javascript crypto added to SSL is a great way to let your errors insert vunerabilities on an otherwise secure page.

by DCKing 12y ago

valarauca1 12y ago

The weakness of Diffie-Hellman is authentication not the algorithm itself. >Nonsense, it's not obfuscation. The issue with in browser JS you seem to be completely missing is if you can't trust the network to deliver your message. How can you trust it to deliver your crypto unchanged, un-tampered, etc? The answer is you can't. If you create a system where you can, you render your crypto unnecessary.

DCKing 12y ago
1. The weakness of plain Diffie-Hellman is that the data you receive (the other part of the key exchange) can be from someone you can't trust. You shouldn't use plain Diffie-Hellman if your attack model includes active attackers on the network. The weakness of JS crypto is that the data you receive (the JS crypto library) can be from someone you can't trust. You shouldn't use JS crypto if your attack model includes active attackers on the network. See what I did there? 2. Under the attack model of the passive eavesdropper, the assumption is that the crypto works because the passive eavesdropper does not tamper with JavaScript. Was this not clear from my previous posts?
- valarauca1 12y ago
  >[...]can be from someone you can't trust. So authentication? We are talking about Authentication right? Because I said that. The weakness of DHE is that you can't authenticate who are you are talking too. >You shouldn't use JS crypto if your attack model includes active attackers on the network. A crypto model has to include every possible attack vector. Crypto isn't something that happens in a vacuum. You assume the worst always. If you ever say, "No, nobody would go that far" you aren't doing crypto, your doing obfuscation. Once a message leaves your hand, everything that can go wrong, will go wrong. In crypto research people suggested moving away from SHA-1 because an attack was found, not because it was remotely possible but because it logically and mathematically existed. Crypto is about numbers and logics, not models and cost expense analysis, and what an attacker could do. Obfuscation is a game of frustration where you create a bar, and keep raising it. Your system is fundamentally broken, but you count on people getting frustrated, or bored. Before they break it. Its game of wits. :.:.: The system you're talking about isn't crypto. Its obfuscation. Your counting on somebody not moving beyond A,B, and C. Getting frustrated and giving up. Crypto doesn't do that.
  - DCKing 12y ago
    The weakness of JS Crypto is that you cannot authenticate the source of your crypto library so you cannot make sure it works properly. The problems are equivalent. All your ranting against what I'm saying is also directly applicable to plain Diffie-Hellman. Both simply are not secure under the active attacker model. That does not disqualify plain Diffie-Hellman from having some use (although not under most attack models), and that does not disqualify JS crypto from having some use (although not under most attack models). I'm going to respectfully decline discussing what attack models are and their use in security protocols on HN, as you unfortunately appear to not understand what I mean (which is probably my fault) or what attack models are used for in security research. You also appear to be confusing security research and cryptography research. You can mail me if you want to discuss this further.
    - valarauca1 12y ago
      >The weakness of JS Crypto is that you cannot authenticate the source of your crypto library so you cannot make sure it works properly One of many, this isn't the only issue. Even if you authenticate the host what prevents tampering via MitM attacks? > All your ranting against what I'm saying is also directly applicable to plain Diffie-Hellman yes and no. Standard white paper Diffie-Hellman yes. But implementations can fix that. As you point out. >That does not disqualify plain Diffie-Hellman from having some use except >and that does not disqualify JS crypto from having some use Wrong. Because you keep dodging my main point. Anything that solves the problem of: 1) Is who your talking to the right person (authentication)? 2) Is your code arriving unchanged (authentication + encryption)? The two main issues with JS crypto. Solves what ever problem your trying to solve with JS crypto. And any solution that allows you create secure JS client side crypto, fundamentally makes it obsolete. That's the problem I'm going on about.
      - DCKing 12y ago
        > yes and no. Standard white paper Diffie-Hellman yes. But implementations can fix that. As you point out. Well, there we have it. I happen to have worked on a project where plain Diffie-Hellman was used not long ago. The active attacker model was genuinely not a threat/solved by other methods in this particular context, and simple confidentiality provided by a plain Diffie-Hellman key exchange was enough. As another example, plain Diffie-Hellman is also used in SSH sessions without predistributed keys [1]. Clearly, the presence of active attackers is not always a problem in the real world! If that is the case, then there also exist legitimate uses for JS crypto [2]. As a sidenote nitpick, no implementation of plain Diffie-Hellman can fix the authentication issue. There are instead variations built upon plain Diffie-Hellman (notably authenticated Diffie-Hellman) that solve the authentication issue. But these protocols are not the same as plain Diffie-Hellman. [1] RFC 4253, section 8 [2] I feel that I should stress again that although this is true for these particular use cases, JS crypto should not be trusted in general.
gnur 12y ago
Sometimes you don't need the data to be decrypted on the host. Your crypte is still useful if the host doesn't want to decrypt anything. Javascript crypto as an alternative to SSL makes no sence, an implementation in which the server never gets the plaintext is currently only possible with client side javascript crypto.
- danielweber 12y ago
  I agree that any discussion of using JavaScript-crypto instead of SSL is nuts and likely a strawman complaint. But just because it's "the best we can do," that doesn't mean it's a good idea. EDIT 1 minute before I made this comment 'tptacek said the fallacy better elsewhere on this page "we really need browser crypto to work, therefore it works"."
- marcosdumay 12y ago
  Javascript crypto added to SSL is a great way to let your errors insert vunerabilities on an otherwise secure page.