<story><title>Practical attack against TLS/SSL and RC4</title><url>http://www.rc4nomore.com/?hn</url></story><parent_chain><item><author>theandrewbailey</author><text>While I agree that RC4 should die in a fire, this attack seems impractical to me.&lt;p&gt;&amp;gt; To successfully decrypt a 16-character cookie with a success probability of 94%, roughly 9x2^27 encryptions of the cookie need to be captured. Since we can make the client transmit 4450 requests per seconds, this amount can be collected in merely 75 hours.&lt;p&gt;How likely would that amount of network traffic and energy consumption cue the potential victim that something malicious is going on?</text></item></parent_chain><comment><author>tomvangoethem</author><text>Colleague of the author here.&lt;p&gt;I guess that 4450 requests&amp;#x2F;s to one IP, or even spread across multiple IPs, could trigger some alarms if the victim is alert. Unfortunately, I&amp;#x27;m not that familiar with IDS&amp;#x2F;IPS&amp;#x27;s to answer that with much confidence.&lt;p&gt;In any case, an attacker has a lot of options. The requests do not need to be made sequentially, so an attacker could basically start and resume his attack whenever he wants, e.g. when the victim is away from keyboard (which he can estimate based on the network traffic someone usually generates). An attacker could also simply slow down the number of requests&amp;#x2F;s, although this results in a larger number of hours required for a successful attack.&lt;p&gt;As for energy&amp;#x2F;CPU consumption, I don&amp;#x27;t think that&amp;#x27;d be a big concern. When the practical attack was performed, the CPU usage went up to around 75%, still allowing one to visit other websites without noticing anything. So unless one would closely monitor the CPU&amp;#x2F;network usage, I don&amp;#x27;t think the average victim would notice it.</text></comment>
<story><title>Practical attack against TLS/SSL and RC4</title><url>http://www.rc4nomore.com/?hn</url></story><parent_chain><item><author>theandrewbailey</author><text>While I agree that RC4 should die in a fire, this attack seems impractical to me.&lt;p&gt;&amp;gt; To successfully decrypt a 16-character cookie with a success probability of 94%, roughly 9x2^27 encryptions of the cookie need to be captured. Since we can make the client transmit 4450 requests per seconds, this amount can be collected in merely 75 hours.&lt;p&gt;How likely would that amount of network traffic and energy consumption cue the potential victim that something malicious is going on?</text></item></parent_chain><comment><author>X-Istence</author><text>Impractical or not, this is still showing a possible attack.&lt;p&gt;Let&amp;#x27;s say the client leaves their computer on at work over a long weekend ...&lt;p&gt;The collision attacks against MD5 were at first also claimed to be impractical...</text></comment>