Comments on: MD5 – The hash algorithm is now Broken!!! http://cryptocrats.com/crypto/md5-the-hash-algorithm-is-now-broken/ Mon, 12 Jan 2009 16:49:43 -0600 http://wordpress.org/?v=2.8.6 hourly 1 By: Vivek Athalye http://cryptocrats.com/crypto/md5-the-hash-algorithm-is-now-broken/comment-page-1/#comment-202 Vivek Athalye Mon, 12 Jan 2009 16:49:43 +0000 http://cryptocrats.com/?p=157#comment-202 hmm... an interesting dilemma ... to trust or not to trust, is the question!! well, thank you for explaining the pros and cons of showing warnings / errors. and i look forward to ubiquitous new standards and processes that will help the end user to trust genuine sites/documents without much efforts. hmm… an interesting dilemma …
to trust or not to trust, is the question!!

well, thank you for explaining the pros and cons of showing warnings / errors.

and i look forward to ubiquitous new standards and processes that will help the end user to trust genuine sites/documents without much efforts.

]]> By: Aniruddha Shrotri http://cryptocrats.com/crypto/md5-the-hash-algorithm-is-now-broken/comment-page-1/#comment-199 Aniruddha Shrotri Mon, 12 Jan 2009 05:56:17 +0000 http://cryptocrats.com/?p=157#comment-199 You have a point, but there is really no substitute for end user's education. Software alone cannot address all the security concerns all the time. An example is spam detection software -- typically it is able to detect what is definitely a spam, but occasionally has only a probabilistic idea about some mails and in that case it is left to the user to determine if he/she considers it spam. Browsers giving an alert for anything found suspect with the certificate will certainly warn the user that there is something potentially wrong with the certificate. In such a case the user should, based on external factors such as user's familiarity with the website, the criticality of the content that the site is giving etc., decide for himself whether he wants to trust such a site. The applications could, actually given an error instead of warning, but that has the danger that potentially a very few minority of sites which use such genuine certificates might become inaccessible. Truely speaking, the problem is not so grave for SSL and websites, but is a little complex for signed documents. That is because, likewise, there is this issue of what should an application do if it finds MD5 (or for that matter MD2 or MD4) in a digital signature or certificate -- should it only give a warning or fail the signature verification altogether? If it gave only a warning, one might have the same question -- what should an end user do with a warning. On the other hand if it treats it as error, potentially a lot of genuine signed documents might lose their authenticity. I believe that just because an algorithm has been broken (or some key lengths have become weak), it would be too much of a penalty to pay if it rendered all information that uses such algorithms or keys useless. Again, here external factors should come into picture based on which the receiver of the information could decide whether to trust the information or not. To precisely address such needs, some standardization bodies are working on defining standards for long term archiving. Some signed documents need to be stored for a long time like 10, 20 or 30 years and one needs to ensure their authenticity at that time. What happens to signed documents over a period of time when the algorithms get broken or keys become weak. Essentially the standards talk about using trusted third party timestamps to clearly mark the time when the signature was done, and then re-signing periodically such documents with latest algorithms and key lengths which are not broken. However, such standards are far from being in deployment and until such times as these standards become ubiquitus, users will have to depend on some external factors to take a call about the trustworthiness of information. You have a point, but there is really no substitute for end user’s education. Software alone cannot address all the security concerns all the time. An example is spam detection software — typically it is able to detect what is definitely a spam, but occasionally has only a probabilistic idea about some mails and in that case it is left to the user to determine if he/she considers it spam. Browsers giving an alert for anything found suspect with the certificate will certainly warn the user that there is something potentially wrong with the certificate. In such a case the user should, based on external factors such as user’s familiarity with the website, the criticality of the content that the site is giving etc., decide for himself whether he wants to trust such a site. The applications could, actually given an error instead of warning, but that has the danger that potentially a very few minority of sites which use such genuine certificates might become inaccessible.

Truely speaking, the problem is not so grave for SSL and websites, but is a little complex for signed documents. That is because, likewise, there is this issue of what should an application do if it finds MD5 (or for that matter MD2 or MD4) in a digital signature or certificate — should it only give a warning or fail the signature verification altogether? If it gave only a warning, one might have the same question — what should an end user do with a warning. On the other hand if it treats it as error, potentially a lot of genuine signed documents might lose their authenticity. I believe that just because an algorithm has been broken (or some key lengths have become weak), it would be too much of a penalty to pay if it rendered all information that uses such algorithms or keys useless. Again, here external factors should come into picture based on which the receiver of the information could decide whether to trust the information or not.

To precisely address such needs, some standardization bodies are working on defining standards for long term archiving. Some signed documents need to be stored for a long time like 10, 20 or 30 years and one needs to ensure their authenticity at that time. What happens to signed documents over a period of time when the algorithms get broken or keys become weak. Essentially the standards talk about using trusted third party timestamps to clearly mark the time when the signature was done, and then re-signing periodically such documents with latest algorithms and key lengths which are not broken. However, such standards are far from being in deployment and until such times as these standards become ubiquitus, users will have to depend on some external factors to take a call about the trustworthiness of information.

]]> By: Vivek Athalye http://cryptocrats.com/crypto/md5-the-hash-algorithm-is-now-broken/comment-page-1/#comment-197 Vivek Athalye Sat, 10 Jan 2009 15:04:32 +0000 http://cryptocrats.com/?p=157#comment-197 indeed its scary ... In the last point u mentioned that applications should flag a warning if they find "unknown extension"... but even if such a warning is given to user, how will it help? end user like me, will be in no position to make any sense out of the contents of the extension. You would have seen lot of sites that show the screen shots of the warning dialogs (typically on download sites or if some activeX needs to be installed) and "guide" the user to continue the operation / process. What if a fraud site "guides" the user in same way to get rid of the warning dialog, how are we going to handle it?? indeed its scary …

In the last point u mentioned that applications should flag a warning if they find “unknown extension”… but even if such a warning is given to user, how will it help? end user like me, will be in no position to make any sense out of the contents of the extension.

You would have seen lot of sites that show the screen shots of the warning dialogs (typically on download sites or if some activeX needs to be installed) and “guide” the user to continue the operation / process. What if a fraud site “guides” the user in same way to get rid of the warning dialog, how are we going to handle it??

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