Cryptpad: Zero Knowledge, Collaborative Real Time Editing • Hacker News Board

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#31

Post by gry » Fri, Sep 23, 2016, 7:55 PM UTC

anarcat wrote: post #28

no_protocol wrote: post #5

I have often seen claims that doing any kind of crypto in (browser) javascript is dangerous. Does this fall into that trap? How can I safely share the URL to someone without already using an established encrypted communication method? Is the encryption key stored in my browser history?

yes. you can't. and yes.

While the ideas and implementation are neat, this suffers from the chicken and egg problem[1]. You have to trust server's resources are not tampered with. Adding an event binding to tamper or siphon data before it's encrypted is simple.

[1] https://www.nccgroup.trust/us/about-us/newsroom-and-events/b...

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#32

Post by franciscop » Fri, Sep 23, 2016, 7:57 PM UTC

I did something like this 3-4 years ago, it was in secretdiary.com (or .org), now with different people. The main difference is that the url fragment had two parts:

http://secretdiary.org/#IDENTIFIER-AUTOGENPASSWORD

The autogenerated password was optional (and random) and you could instead require a password. This way it was not GET-cached anywhere unless you wanted it to so you could share the actual URL anywhere with no fear of it leaking the secrets, or you could just share the whole thing similarly to cryptpad.fr

However it was one of my first projects so it didn't even had https.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#33

Post by whamlastxmas » Fri, Sep 23, 2016, 8:08 PM UTC

no_protocol wrote: post #23

Ar-Curunir wrote: post #17

Why do people insist on using the term zero knowledge for simple semantically secure encryption? Zero knowledge has a very specific meaning inside cryptography. Encrypting something does not make it "zero knowledge".

I had the same feeling when reading the copy on the site. I looked for an explanation of what they mean by the statement, but couldn't find one. Google led me to a Spider Oak page that seems to use the terminology in a similar manner [1]. I have a hard time even accepting this definition of "zero knowledge' on its own, separate from the existing cryptographic one. Wouldn't the host at least know things like the size…

File size and date sent is probably only useful if someone is specifically targeting you, and it's virtually guaranteed that the only person who wound target someone specifically and also be able to make use of that data is a government agency. In that case they'd be able to monitor your data at an ISP level anyway, making it moot. It doesn't look like Spideroak takes bitcoin payments anyway, making this even further moot. Anyone serious about privacy against state actors wouldn't use it.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#34

Post by celticninja » Fri, Sep 23, 2016, 8:18 PM UTC

ar0 wrote: post #14

celticninja wrote: post #4

Sharing the URL is essentially giving out the key, so there is no digitally safe way to do this unless you encrypt the initial message, at which stage you are using encrypted communication anyway and the URL just leaves open an attack vector. Please correct me if I am wrong.

Yes, you need an encrypted (or local) channel to share the Cryptpad URL but this can be achieved by using e.g. PGP or Signal or any other of the encrypted messengers out there. However, being able to send an encrypted message to someone is not the same as being able to collaboratively edit documents in real time (think "Google Docs") with that person. This is where the value-added of Cryptpad lies: Yes, you need to a…

I did not mean it was nothing, I was juts seeing if I understood how it works and the risks. But I can see how a collaborative doc would be useful, this would be a good alternative to the shared Gmail account communicate with draft messages option.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#35

Post by coldwaterq » Fri, Sep 23, 2016, 8:22 PM UTC

whamlastxmas wrote: post #33

no_protocol wrote: post #23

Earlier quoted context omitted.

I had the same feeling when reading the copy on the site. I looked for an explanation of what they mean by the statement, but couldn't find one. Google led me to a Spider Oak page that seems to use the terminology in a similar manner [1]. I have a hard time even accepting this definition of "zero knowledge' on its own, separate from the existing cryptographic one. Wouldn't the host at least know things like the size…

File size and date sent is probably only useful if someone is specifically targeting you, and it's virtually guaranteed that the only person who wound target someone specifically and also be able to make use of that data is a government agency. In that case they'd be able to monitor your data at an ISP level anyway, making it moot. It doesn't look like Spideroak takes bitcoin payments anyway, making this even further…

I don't agree that only government agencies would care. For example, anyone on open wifi can be easily targeted. So anyone doing something at a university could be targeted. I would imagine that some corporation would be interested in something from a university enough to try this.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#36

Post by no_protocol » Fri, Sep 23, 2016, 8:27 PM UTC

whamlastxmas wrote: post #33

no_protocol wrote: post #23

Earlier quoted context omitted.

I had the same feeling when reading the copy on the site. I looked for an explanation of what they mean by the statement, but couldn't find one. Google led me to a Spider Oak page that seems to use the terminology in a similar manner [1]. I have a hard time even accepting this definition of "zero knowledge' on its own, separate from the existing cryptographic one. Wouldn't the host at least know things like the size…

File size and date sent is probably only useful if someone is specifically targeting you, and it's virtually guaranteed that the only person who wound target someone specifically and also be able to make use of that data is a government agency. In that case they'd be able to monitor your data at an ISP level anyway, making it moot. It doesn't look like Spideroak takes bitcoin payments anyway, making this even further…

Useful or not, I consider the boldface statement

> we know nothing about the encrypted data you store on our servers

misleading, since they do know some things about the encrypted data.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#37

Post by Ar-Curunir » Fri, Sep 23, 2016, 8:42 PM UTC

infodroid wrote: post #29

Ar-Curunir wrote: post #17

Why do people insist on using the term zero knowledge for simple semantically secure encryption? Zero knowledge has a very specific meaning inside cryptography. Encrypting something does not make it "zero knowledge".

> Why do people insist on using the term zero knowledge for simple semantically secure encryption? Note that in the domain of privacy-enhancing technologies the term "zero-knowledge" does not refer to "semantically secure encryption". Instead it is used to mean that a service provider does not have access to user data, and that this claim can be proven cryptographically. The use of the term zero-knowledge to promote…

Note that in the field of cryptography, the term zero knowledge refers to zero knowledge proofs, which predate that company by over 13 years.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#38

Post by willvarfar » Fri, Sep 23, 2016, 8:46 PM UTC

whamlastxmas wrote: post #33

no_protocol wrote: post #23

Earlier quoted context omitted.

I had the same feeling when reading the copy on the site. I looked for an explanation of what they mean by the statement, but couldn't find one. Google led me to a Spider Oak page that seems to use the terminology in a similar manner [1]. I have a hard time even accepting this definition of "zero knowledge' on its own, separate from the existing cryptographic one. Wouldn't the host at least know things like the size…

File size and date sent is probably only useful if someone is specifically targeting you, and it's virtually guaranteed that the only person who wound target someone specifically and also be able to make use of that data is a government agency. In that case they'd be able to monitor your data at an ISP level anyway, making it moot. It doesn't look like Spideroak takes bitcoin payments anyway, making this even further…

Metadata is often more useful than the message, and sometimes can expose the message. For example, a collaborative editor had better not send each key press to the other editors else timing attacks can reconstruct probable text fragments etc.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#39

Post by infodroid » Fri, Sep 23, 2016, 8:54 PM UTC

Ar-Curunir wrote: post #37

infodroid wrote: post #29

Earlier quoted context omitted.

> Why do people insist on using the term zero knowledge for simple semantically secure encryption? Note that in the domain of privacy-enhancing technologies the term "zero-knowledge" does not refer to "semantically secure encryption". Instead it is used to mean that a service provider does not have access to user data, and that this claim can be proven cryptographically. The use of the term zero-knowledge to promote…

Note that in the field of cryptography, the term zero knowledge refers to zero knowledge proofs, which predate that company by over 13 years.

I don't dispute that fact. But there is precedent for the use of the term in privacy-respecting services, so we shouldn't be surprised when we encounter it. After ZKS shut down, the term continued to be used by hosting and communications services to explain their value proposition in a simple way.

Having said that, I agree with the point that nowadays this usage may be unhelpful in promoting privacy-respecting services because zero-knowledge proofs have come a long way and there are now services like Zerocash that actually make use of them. So using the term to promote a different privacy-respecting feature may be confusing or misleading.

Re: Cryptpad: Zero Knowledge, Collaborative Real Time Editing

#40

Post by SilasX » Fri, Sep 23, 2016, 9:23 PM UTC

infodroid wrote: post #39

Ar-Curunir wrote: post #37

Earlier quoted context omitted.

Note that in the field of cryptography, the term zero knowledge refers to zero knowledge proofs, which predate that company by over 13 years.

I don't dispute that fact. But there is precedent for the use of the term in privacy-respecting services, so we shouldn't be surprised when we encounter it. After ZKS shut down, the term continued to be used by hosting and communications services to explain their value proposition in a simple way. Having said that, I agree with the point that nowadays this usage may be unhelpful in promoting privacy-respecting servic…

I wish they would pick a clearer term that's not already in use, like (as I think they mean in this case) "provider-obscured". Heck, even "homomorphic" would be better, as that signifies "does stuff you want with your data, without knowing the content of said data".