This claims to be well-documented and secure by default, but I cannot find a link to the documentation (or is it just the README)? What actual algorithm is used for encryption and for signing?
The README has a major red flag:
> From the math perspective, there is no difference between private and public keys, they both can be used to encrypt messages that only can de be decrypted by the other. Most of the security tools, including enc, artificially forbid using the public key for decrypting messages because that's not how it should be used (encrypting messages that anyone can decrypt is pointless).
Most security tools forbid that because it is dangerous! Also, this description sounds like textbook RSA is being used...
Oh absolutely, the theory behind QKD is fascinating! And I do think that some day there may be actually secure practical implementations, maybe even ones that are practical for more than a few niche applications.
But you mentioned the assumptions on the implementation, not on the underlying mathematics. The thing that concerns me is that QKD introduces additional hardware to operate, and there have been many demonstrations of weaknesses in that hardware that threaten the overall security of the system. With DIQKD you ensure that those issues no longer affect security (again it is absolutely remarkable that this is possible at all),
but now you still have to concern yourself with all the implementation vulnerabilities that also plague classical cryptography. In that sense I mean that the implementation assumptions are now the same.
Yes, otherwise how would you know you are indeed communicating with that party?
Otherwise the standard Person-in-the-Middle attack would apply: Eve (claiming to be Bob) first runs a full protocol session (quantum + classical communication) with Alice, resulting in a shared key X. Then she does the same to Bob, resulting in a key Y. When Alice wants to encrypt a message to Bob, she encrypts with X. Eve can decrypt (and optionally re-encrypt with Y and forward the message to Bob).
> Rather, device-independent quantum key distribution allows you to scale back the assumptions on your implementation to a well-motivated, minimal set. To me, this is already intriguing enough without the need for hyperbole!
Would it be accurate to say it is scaled back to the level achieved by classical (non-quantum) cryptography?
The article suggests that quantum key distribution (QKD) is a replacement for a courier, but that is not true. Distributing an initial small secret key (which allows authenticity of the post-processing of the quantum measurements) is still required.
Also I think the added value of device-independence is overstated. While it does indeed prevent loss of security by faulty quantum hardware (even if constructed maliciously), there is still a lot of classical post-processing required. That device still needs to be trusted.
For example, when the device is outputting the shared key, it still needs to be trusted that it isn't also delivering that key back to Eve.
The README has a major red flag:
> From the math perspective, there is no difference between private and public keys, they both can be used to encrypt messages that only can de be decrypted by the other. Most of the security tools, including enc, artificially forbid using the public key for decrypting messages because that's not how it should be used (encrypting messages that anyone can decrypt is pointless).
Most security tools forbid that because it is dangerous! Also, this description sounds like textbook RSA is being used...