Re: [Bitcoin-development] Time
Ok... 'time' on the blockchain could be 'gamed' ... but with great difficulty. Unfortunately not: miners have in the past routinely gamed the timestamp in order to use it as an extra nonce and squeeze some more gigahashes out of their hardware/pool. Also remember that currently the chain could be dominated by a coalition of just two pools. An application presented with a fake blockchain can use quite a few heuristics to test the 'validity' of the block chain. The app cannot tell if it was given a truncated chain. You could keep such an app stuck in the past forever. This is often a problem. Reliable 'time' has been impossible up until now - because you need to trust the time source, and that can always be faked. Using the blockchain as an approximate time source gives you a world wide consensus without direct trust of any player. Much though I hate to be a party pooper, you could currently get Bitcoin-level trusted time by just polling at least two or three independent servers e.g. google.com, baidu.cn, yandex.ru(they all serve time via HTTPS headers). If we crack the mining decentralisation problem then this argument becomes a lot stronger, but for now .. So if this presumption is correct, then we can now build time capsule applications that can not be tricked into exposing their contents too early by running them in a virtual environment with the wrong system time. If you have a tamper resistant execution environment (TXT, SGX, Flicker etc) then yes. However trusted execution environments sometimes have tamper resistant clocks as well for exactly this reason. So whether this technique makes sense depends a lot on the details of your configuration, I think. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Time
Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt. On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine vois...@gmail.com wrote: It's based on the block height, not the block's timestamp. If you have access to the device and the phone itself is not pin locked, then you can jailbreak it and get access to the wallet seed that way. A pin locked device however is reasonably secure as the filesystem is hardware aes encrypted to a combination of pin+uuid. This was just an easy way to prevent multiple pin guesses by changing system time in settings, so that isn't the weakest part of the security model. Aaron Voisine breadwallet.com On Thu, Jul 24, 2014 at 8:21 PM, William Yager will.ya...@gmail.com wrote: On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell gmaxw...@gmail.com wrote: Is breadwallet tamper resistant zero on tamper hardware? otherwise this sounds like security theater I attach a debugger to the process (or modify the program) and ignore the block sourced time. It's an iOS application. I would imagine it is substantially more difficult to attach to a process (which, at the very least, requires root, and perhaps other things on iOS) than to convince the device to change its system time. That said, the security benefits might not be too substantial. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Time
The problem is if someone moves system time forward between app launches. The lockout period doesn't have to be all that precise, it just makes you wait for the next block, then 5, then 25, and so on. Using a well known time server over https would also be a good option, but the wallet app already has the chain height anyway. On Friday, July 25, 2014, Mike Hearn m...@plan99.net wrote: Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt. On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine vois...@gmail.com javascript:_e(%7B%7D,'cvml','vois...@gmail.com'); wrote: It's based on the block height, not the block's timestamp. If you have access to the device and the phone itself is not pin locked, then you can jailbreak it and get access to the wallet seed that way. A pin locked device however is reasonably secure as the filesystem is hardware aes encrypted to a combination of pin+uuid. This was just an easy way to prevent multiple pin guesses by changing system time in settings, so that isn't the weakest part of the security model. Aaron Voisine breadwallet.com On Thu, Jul 24, 2014 at 8:21 PM, William Yager will.ya...@gmail.com javascript:_e(%7B%7D,'cvml','will.ya...@gmail.com'); wrote: On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell gmaxw...@gmail.com javascript:_e(%7B%7D,'cvml','gmaxw...@gmail.com'); wrote: Is breadwallet tamper resistant zero on tamper hardware? otherwise this sounds like security theater I attach a debugger to the process (or modify the program) and ignore the block sourced time. It's an iOS application. I would imagine it is substantially more difficult to attach to a process (which, at the very least, requires root, and perhaps other things on iOS) than to convince the device to change its system time. That said, the security benefits might not be too substantial. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net javascript:_e(%7B%7D,'cvml','Bitcoin-development@lists.sourceforge.net'); https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net javascript:_e(%7B%7D,'cvml','Bitcoin-development@lists.sourceforge.net'); https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Aaron Voisine breadwallet.com -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Time
Sorry, you're right. I'd have hoped a delay that doubles on failure each time up to some max would be good enough, relying on the p2p network to unlock a PIN feels weird, but I can't really quantify why or what's wrong with it so I guess it's just me :-) On Fri, Jul 25, 2014 at 4:45 PM, Aaron Voisine vois...@gmail.com wrote: The problem is if someone moves system time forward between app launches. The lockout period doesn't have to be all that precise, it just makes you wait for the next block, then 5, then 25, and so on. Using a well known time server over https would also be a good option, but the wallet app already has the chain height anyway. On Friday, July 25, 2014, Mike Hearn m...@plan99.net wrote: Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt. On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine vois...@gmail.com wrote: It's based on the block height, not the block's timestamp. If you have access to the device and the phone itself is not pin locked, then you can jailbreak it and get access to the wallet seed that way. A pin locked device however is reasonably secure as the filesystem is hardware aes encrypted to a combination of pin+uuid. This was just an easy way to prevent multiple pin guesses by changing system time in settings, so that isn't the weakest part of the security model. Aaron Voisine breadwallet.com On Thu, Jul 24, 2014 at 8:21 PM, William Yager will.ya...@gmail.com wrote: On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell gmaxw...@gmail.com wrote: Is breadwallet tamper resistant zero on tamper hardware? otherwise this sounds like security theater I attach a debugger to the process (or modify the program) and ignore the block sourced time. It's an iOS application. I would imagine it is substantially more difficult to attach to a process (which, at the very least, requires root, and perhaps other things on iOS) than to convince the device to change its system time. That said, the security benefits might not be too substantial. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Aaron Voisine breadwallet.com -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Time
Probably because the network isn't designed for interactive proofs. Most interactive algoritms AFAICT requires that some machine holds a secret state (or at least continuous and untampered state, but you still need to verify you're falling to the right machine), otherwise the machine can be mimicked and rewound to earlier states. Without a challenge-response that can't be faked, you've got problems. There's no trusted machines here that you can rely on. The certainty of having the right blockchain is a statistical one over longer periods of time, not enough for a PIN you want verified right now. So you can always be shown an old copy, and if your node isn't up to date yet then it can also be shown fake chains further into the future. Maybe you could throw in some kind of Secure Multiparty Computation among the miners to enable challenge-response, with state saved in the blockchain (so it can't be rolled back), but that would be fragile. How do you select what nodes may participate? How do you prevent the secret state from leaking? And performance would be absolutely horrible, and reliability is a huge problem. Den 25 jul 2014 18:03 skrev Mike Hearn m...@plan99.net: Sorry, you're right. I'd have hoped a delay that doubles on failure each time up to some max would be good enough, relying on the p2p network to unlock a PIN feels weird, but I can't really quantify why or what's wrong with it so I guess it's just me :-) On Fri, Jul 25, 2014 at 4:45 PM, Aaron Voisine vois...@gmail.com wrote: The problem is if someone moves system time forward between app launches. The lockout period doesn't have to be all that precise, it just makes you wait for the next block, then 5, then 25, and so on. Using a well known time server over https would also be a good option, but the wallet app already has the chain height anyway. On Friday, July 25, 2014, Mike Hearn m...@plan99.net wrote: Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt. On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine vois...@gmail.com wrote: It's based on the block height, not the block's timestamp. If you have access to the device and the phone itself is not pin locked, then you can jailbreak it and get access to the wallet seed that way. A pin locked device however is reasonably secure as the filesystem is hardware aes encrypted to a combination of pin+uuid. This was just an easy way to prevent multiple pin guesses by changing system time in settings, so that isn't the weakest part of the security model. Aaron Voisine breadwallet.com On Thu, Jul 24, 2014 at 8:21 PM, William Yager will.ya...@gmail.com wrote: On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell gmaxw...@gmail.com wrote: Is breadwallet tamper resistant zero on tamper hardware? otherwise this sounds like security theater I attach a debugger to the process (or modify the program) and ignore the block sourced time. It's an iOS application. I would imagine it is substantially more difficult to attach to a process (which, at the very least, requires root, and perhaps other things on iOS) than to convince the device to change its system time. That said, the security benefits might not be too substantial. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Aaron Voisine breadwallet.com -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub!
Re: [Bitcoin-development] Time
Yes, if the wallet isn't up to date yet, it uses the highest estimated block height from connected peers, but that could be gamed by controlling the network. The app has blockchain checkpoints in it though, so you couldn't truncate the chain starting point below that. The worst case is that you get a 4-5 extra guesses, but as I mentioned, it'd be easier to just jailbreak the phone if the phone itself isn't using a system wide pin lock. I just though it was a fun and convenient way to prevent the system time hack. The system pin is what protects your wallet in the event of physical theft, and the app pin is just for when you lend your phone to a friend for a few minutes. Aaron Voisine breadwallet.com On Fri, Jul 25, 2014 at 9:22 AM, Natanael natanae...@gmail.com wrote: Probably because the network isn't designed for interactive proofs. Most interactive algoritms AFAICT requires that some machine holds a secret state (or at least continuous and untampered state, but you still need to verify you're falling to the right machine), otherwise the machine can be mimicked and rewound to earlier states. Without a challenge-response that can't be faked, you've got problems. There's no trusted machines here that you can rely on. The certainty of having the right blockchain is a statistical one over longer periods of time, not enough for a PIN you want verified right now. So you can always be shown an old copy, and if your node isn't up to date yet then it can also be shown fake chains further into the future. Maybe you could throw in some kind of Secure Multiparty Computation among the miners to enable challenge-response, with state saved in the blockchain (so it can't be rolled back), but that would be fragile. How do you select what nodes may participate? How do you prevent the secret state from leaking? And performance would be absolutely horrible, and reliability is a huge problem. Den 25 jul 2014 18:03 skrev Mike Hearn m...@plan99.net: Sorry, you're right. I'd have hoped a delay that doubles on failure each time up to some max would be good enough, relying on the p2p network to unlock a PIN feels weird, but I can't really quantify why or what's wrong with it so I guess it's just me :-) On Fri, Jul 25, 2014 at 4:45 PM, Aaron Voisine vois...@gmail.com wrote: The problem is if someone moves system time forward between app launches. The lockout period doesn't have to be all that precise, it just makes you wait for the next block, then 5, then 25, and so on. Using a well known time server over https would also be a good option, but the wallet app already has the chain height anyway. On Friday, July 25, 2014, Mike Hearn m...@plan99.net wrote: Given that the speed at which the block chain advances is kind of unpredictable, I'd think it might be better to just record the time to disk when a PIN attempt is made and if you observe time going backwards, refuse to allow more attempts until it's advanced past the previous attempt. On Fri, Jul 25, 2014 at 7:56 AM, Aaron Voisine vois...@gmail.com wrote: It's based on the block height, not the block's timestamp. If you have access to the device and the phone itself is not pin locked, then you can jailbreak it and get access to the wallet seed that way. A pin locked device however is reasonably secure as the filesystem is hardware aes encrypted to a combination of pin+uuid. This was just an easy way to prevent multiple pin guesses by changing system time in settings, so that isn't the weakest part of the security model. Aaron Voisine breadwallet.com On Thu, Jul 24, 2014 at 8:21 PM, William Yager will.ya...@gmail.com wrote: On Thu, Jul 24, 2014 at 10:39 PM, Gregory Maxwell gmaxw...@gmail.com wrote: Is breadwallet tamper resistant zero on tamper hardware? otherwise this sounds like security theater I attach a debugger to the process (or modify the program) and ignore the block sourced time. It's an iOS application. I would imagine it is substantially more difficult to attach to a process (which, at the very least, requires root, and perhaps other things on iOS) than to convince the device to change its system time. That said, the security benefits might not be too substantial. -- Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Want fast and easy access to all the code in your
