Re: Who cares about side-channel attacks?
Wouter Slegers [EMAIL PROTECTED] writes: Timing analysis is quite possible to pull of in straightforward implementations as demonstrated over the Internet on OpenSSL prior to their implementation of blinding ( http://crypto.stanford.edu/~dabo/papers/ssl-timing.pdf). But frankly, I have never heard of such an attack actually being used in the field. Real side channel analysis (DPA, EMA etc) seems mostly limited to academics and labs, not the field. One of the XBox attacks, allowing rollback to a vulnerable kernel, was a timing attack. I'd heard it was also tried in some form (unsuccessfully) against the Wii as part of the breadth-first attack approach. I'm afraid that the best at this moment is mostly rumors. There is some knowledge about attacks in the field but it is spread out a lot and the ones that aggregate this information are not sharing this (it also gives the attackers a view on what works and what not). You can see this with the games-console hacking, the attackers try and release the least amount of information possible so they've got something in reserve when the countermeasures appear. In some cases they use attack method A to find a weakness and then exploit it using unrelated method B, allowing reuse of method A once B is patched by the vendor. As I read his story, he eavesdropped the bus between the bridge chip and the CPU to recover the real bootloader code with the real RC4 key, Sorry, I was referring to two different attacks in the same sentence, and on re-reading managed to make the result quite unclear :-). The timing attack didn't directly recover the authentication key directly but avoided the need to know it, thus allowing unauthorised vulnerable kernels to be loaded. not the incorrect one in the ROM (very nasty trick, kudo's for the Microsoft development team there ;-) ). Often the simplest tricks are the most effective, e.g. stick a PGP header on the data to be protected and the attackers spend forever trying to decrypt it when in fact the processing function is (in pseudocode): seek( file, 16 );// Skip red-herring junk at start processData( file ); (the problem with this one was that they memcpy()'d the fixed header on and the lengths were wrong, but apart from that it would probably have distracted attackers for some time). Peter. - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: Bitcoin P2P e-cash paper
Satoshi Nakamoto wrote: I've been working on a new electronic cash system that's fully peer-to-peer, with no trusted third party. The paper is available at: http://www.bitcoin.org/bitcoin.pdf We very, very much need such a system, but the way I understand your proposal, it does not seem to scale to the required size. For transferable proof of work tokens to have value, they must have monetary value. To have monetary value, they must be transferred within a very large network - for example a file trading network akin to bittorrent. To detect and reject a double spending event in a timely manner, one must have most past transactions of the coins in the transaction, which, naively implemented, requires each peer to have most past transactions, or most past transactions that occurred recently. If hundreds of millions of people are doing transactions, that is a lot of bandwidth - each must know all, or a substantial part thereof. - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: Bitcoin P2P e-cash paper
Satoshi Nakamoto wrote: I've been working on a new electronic cash system that's fully peer-to-peer, with no trusted third party. The paper is available at: http://www.bitcoin.org/bitcoin.pdf We very, very much need such a system, but the way I understand your proposal, it does not seem to scale to the required size. For transferable proof of work tokens to have value, they must have monetary value. To have monetary value, they must be transferred within a very large network - for example a file trading network akin to bittorrent. To detect and reject a double spending event in a timely manner, one must have most past transactions of the coins in the transaction, which, naively implemented, requires each peer to have most past transactions, or most past transactions that occurred recently. If hundreds of millions of people are doing transactions, that is a lot of bandwidth - each must know all, or a substantial part thereof. Long before the network gets anywhere near as large as that, it would be safe for users to use Simplified Payment Verification (section 8) to check for double spending, which only requires having the chain of block headers, or about 12KB per day. Only people trying to create new coins would need to run network nodes. At first, most users would run network nodes, but as the network grows beyond a certain point, it would be left more and more to specialists with server farms of specialized hardware. A server farm would only need to have one node on the network and the rest of the LAN connects with that one node. The bandwidth might not be as prohibitive as you think. A typical transaction would be about 400 bytes (ECC is nicely compact). Each transaction has to be broadcast twice, so lets say 1KB per transaction. Visa processed 37 billion transactions in FY2008, or an average of 100 million transactions per day. That many transactions would take 100GB of bandwidth, or the size of 12 DVD or 2 HD quality movies, or about $18 worth of bandwidth at current prices. If the network were to get that big, it would take several years, and by then, sending 2 HD movies over the Internet would probably not seem like a big deal. Satoshi Nakamoto - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
