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Sorry, I was using security in the sense of physical security that one associates with money, not cryptographic security. But yes, they are both cryptographic p

Sorry, I was using security in the sense of physical security that one associates with money, not cryptographic security. But yes, they are both cryptographic properties of the system and for most systems they are provable properties. If I remember correctly, Chaum's original paper didn't deal with offline double spending. It was blind signature based online e-cash that depend on the bank keeping a list of spent serial numbers(which isn't much easier keeping an account balance). So it's point was mainly anonymity. His subsequent work did offline e-cash with double spend detection, but at least the original paper on that was very inefficient. I'm curious which line of work Digicash tried to deploy. There is a large gap in my knowledge of the literature after that which also handily ignores the work of Stefan Brands, but as far as I know, the first system with really efficient offline double spend detection was due to Camenisch, Hohenberger, and Lysyanskaya, in 2006, long after Digichash went under.

betterunix 13y ago
"If I remember correctly, Chaum's original paper didn't deal with offline double spending. It was blind signature based online e-cash that depend on the bank keeping a list of spent serial numbers(which isn't much easier keeping an account balance). So it's point was mainly anonymity." The point was anonymity and the assurance that double spending is hard. Let's put it this way: how do you know that the attacker cannot create tokens that the bank did not issue, but that the bank will believe are valid? The point of Chaum's original system is that you can prevent such an attack and allow anonymous spending. If the only concern were anonymity, the system would not be hard to create: the bank would just accept everything and the spenders would just create random strings instead of using the withdrawal protocol.

betterunix 13y ago

"If I remember correctly, Chaum's original paper didn't deal with offline double spending. It was blind signature based online e-cash that depend on the bank keeping a list of spent serial numbers(which isn't much easier keeping an account balance). So it's point was mainly anonymity." The point was anonymity and the assurance that double spending is hard. Let's put it this way: how do you know that the attacker cannot create tokens that the bank did not issue, but that the bank will believe are valid? The point of Chaum's original system is that you can prevent such an attack and allow anonymous spending. If the only concern were anonymity, the system would not be hard to create: the bank would just accept everything and the spenders would just create random strings instead of using the withdrawal protocol.