5 ms·
Known-plaintext attack
- belter 5y agoNot to hijack the thread but...If you are reading this you will hopefully enjoy something I submitted a few days ago: https://news.ycombinator.com/item?id=27316630 https://news.ycombinator.com/item?id=27316630
- remram 5y agoWhat is it? Do I have to play the video to find out whether it is relevant?
- belter 5y agoIts a presentation about Colossus and the role it played to help in the cryptanalysis of the Lorenz cipher. It is regarded as "... the world's first programmable, electronic, digital computer, although it was programmed by switches and plugs and not by a stored program..." The presentation has detail of analysis of the different cipher in use at the time. Also fascinating historical details of the technical work done, for example: - Some of the breakthroughs in cryptanalysis were only possible because one day, one of the German Engima machine operators had to resend the same message twice, due to a transmission error. However he/she forgot to rotate the encoding mechanism. - Colossus was considered so secret that after the war it was destroyed on purpose. - The creator of Colossus managed to cross the border and escape the German army just by a 3 hours difference.
- ______- 5y ago> And occurring or believed likely to occur in a different cipher or code message Does anyone know if TLS/HTTPS does padding or tries to alter the length of ciphertext? I ask because a specific length for a specific request that is known to be a certain Wikipedia page (for example: https://en.wikipedia.org/wiki/Islamic_State_of_Iraq_and_the_Levant https://en.wikipedia.org/wiki/Islamic_State_of_Iraq_and_the_...) means certain encrypted request's plaintext are known to an adversary. Is each encrypted network request's ciphertext different or padded to a new size?
- maqp 5y agoAFAIK TLS doesn't make such attempts simply because that would make it quite inefficient. However, if you're using Tor (like you probably should if you want privacy for online browsing) the exit-node that fetches the site for you gets the leaky packet size, and the Tor cell -packets that transit from the exit node to you are static size (500 bytes IIRC). The number of packets can of course be quite revealing too, but all simultaneous data transfer over Tor adds noise to end-to-end correlation on your end.
- beermonster 5y agoPCKS#7 padding IIRC
- jdjgktntnrk 5y agoThis is a classic problem (traffic analysis) that in principle can only be solved by having the browser access random wikipedia pages in a continuous manner, to create cover traffic.
- mrmckizzle 5y agoI'm no expert in cryptography, but don't most versions of TLS/HTTPS use RSA for encryption? Which in turn uses the private/public key methodology to prevent such attacks?
- throwaway525142 5y agoNo AFAIK. The actual traffic is encrypted using a block cipher. Asymmetric crypto is only there to verify each peer's identity and establish a common secret for the symmetric cipher.
- joppy 5y agoThis is right - asymmetric crypto is awesome but just not anywhere near as fast as something like AES for chewing through chunks of data. So some anonymous asymmetric crypto (Diffie-Hellman or similar) is used to set up an encrypted channel, i.e set up a shared AES key, and then RSA is used to verify that the entity on the other end actually holds the private key for that subdomain. After that it’s AES pretty much all the way.
- ExcavateGrandMa 5y agoThe main problem... is binary :Ð nah worries...