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Security never was that big a point with Chaum's e-cash either. It was anonymity. Which it's unclear if anyone values that much. Bitcoin isn't really anonymous

Security never was that big a point with Chaum's e-cash either. It was anonymity. Which it's unclear if anyone values that much. Bitcoin isn't really anonymous and for all the things I hear people saying about Zerocoin, no one has bothered to integrate it.

betterunix 13y ago
Security was and remains an important goal for digital cash. Anonymity in digital cash is a security matter (in fact, anonymity in general is a security matter), and it can be formally defined and a system can be proved to achieve it (not different than other cryptographic security notions). It is also the case the anonymity was not the only security goal; protection against double-spending was equally if not more important, and in systems that support offline transactions there is the notion of protection against "frame ups" i.e. ensuring that the bank cannot produce a proof of double spending if the double spending did not occur.
- anologwintermut 13y ago
  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

Security was and remains an important goal for digital cash. Anonymity in digital cash is a security matter (in fact, anonymity in general is a security matter), and it can be formally defined and a system can be proved to achieve it (not different than other cryptographic security notions). It is also the case the anonymity was not the only security goal; protection against double-spending was equally if not more important, and in systems that support offline transactions there is the notion of protection against "frame ups" i.e. ensuring that the bank cannot produce a proof of double spending if the double spending did not occur.

anologwintermut 13y ago
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.