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>The goal was to prevent spam It does not. Its broken the day someone who can code wants to beak it. >The user is not as affected by the cost... Its exactly

by noxer 5y ago

>The goal was to prevent spam It does not. Its broken the day someone who can code wants to beak it. >The user is not as affected by the cost... Its exactly the opposite it affects the user not an attacker who can generate millions of PoW units on toaster for a few bucks. Or even use another systems idle time. No human needed == its super cheap. Unlike real CAPTCHAs where you need to pay real people to solve them.

postalrat 5y ago
If that was true than why doesn't that person sit down and use his coding talents to optimize bitcoin mining and profit.
- noxer 5y ago
  Not sure if that is joke but Bitcoin mining is already highly optimized and done on scale. Beating the average smartphones in-browser hash power does absolutely nothing. You are not competing against them you compete against large scale mining farms with special hardware.
forestjohnson 5y ago
In short, the Scrypt hash function was designed for this. With SHA256, the "toaster" you were refferring to is called an ASIC and you can buy one for $200 that plugs into a USB port and it would hash faster than 2 million CPUs. However that's not possible with Scrypt, especially with the relatively large memory cost and block size parameters that this software uses. Even GPUs choke on scrypt at these levels. See: https://www.mobsec.ruhr-uni-bochum.de/media/mobsec/arbeiten/2014/12/12/2014-ma-kranz-gpu-scrypt.pdf https://www.mobsec.ruhr-uni-bochum.de/media/mobsec/arbeiten/...
- noxer 5y ago
  You misses the point. It does not matter what kind of technical implementation or algorithm is used. If the average user hardware can solve the "captcha" in a meaningful time on average hardware then an attacker with optimized hardware and on scale can always solve millions of these "captcha" relatively cheap. If you increase hardware demand to slow down an attacker you just exclude more and more legitimate people. Sure the attacker maybe can only spam 500k messages instead of 1MM in the same time but you also reduced the legitimate user by 50%. Even in the absolute worst case where no optimization is possible at all the attacker can still run a device 24/7 so if a normal user has to wait 20 second on a smartphone an attacker can spam at least 4320 messages per day with the same device. And it scale at least perfectly linear. 2 such devices would double the spam capacity.Aand if the block sizes are increased to slow the attacker down it is exactly as much as it slows down the real user. But the real user actually cares and gets annoyed the attacker does not, he keep the same spam/legit message ratio.

by noxer 5y ago

postalrat 5y ago

If that was true than why doesn't that person sit down and use his coding talents to optimize bitcoin mining and profit.

noxer 5y ago
Not sure if that is joke but Bitcoin mining is already highly optimized and done on scale. Beating the average smartphones in-browser hash power does absolutely nothing. You are not competing against them you compete against large scale mining farms with special hardware.

forestjohnson 5y ago

In short, the Scrypt hash function was designed for this. With SHA256, the "toaster" you were refferring to is called an ASIC and you can buy one for $200 that plugs into a USB port and it would hash faster than 2 million CPUs. However that's not possible with Scrypt, especially with the relatively large memory cost and block size parameters that this software uses. Even GPUs choke on scrypt at these levels. See: https://www.mobsec.ruhr-uni-bochum.de/media/mobsec/arbeiten/2014/12/12/2014-ma-kranz-gpu-scrypt.pdf https://www.mobsec.ruhr-uni-bochum.de/media/mobsec/arbeiten/...

noxer 5y ago
You misses the point. It does not matter what kind of technical implementation or algorithm is used. If the average user hardware can solve the "captcha" in a meaningful time on average hardware then an attacker with optimized hardware and on scale can always solve millions of these "captcha" relatively cheap. If you increase hardware demand to slow down an attacker you just exclude more and more legitimate people. Sure the attacker maybe can only spam 500k messages instead of 1MM in the same time but you also reduced the legitimate user by 50%. Even in the absolute worst case where no optimization is possible at all the attacker can still run a device 24/7 so if a normal user has to wait 20 second on a smartphone an attacker can spam at least 4320 messages per day with the same device. And it scale at least perfectly linear. 2 such devices would double the spam capacity.Aand if the block sizes are increased to slow the attacker down it is exactly as much as it slows down the real user. But the real user actually cares and gets annoyed the attacker does not, he keep the same spam/legit message ratio.