3 ms·

Show HN: GoUmbral – ECC arithmetic layer, and soon-to-be proxy re-encryption lib

19 points by tuxxy 8y ago

tuxxy 8y ago
Hey, everyone! For some context, here's our blogpost about this pre-release. We're really excited to debut our cryptography arithmetic layer for Go. It's the first step to making our split-key threshold proxy re-encryption library available in Go. https://blog.nucypher.com/introducing-goumbral-ce979e616359 https://blog.nucypher.com/introducing-goumbral-ce979e616359
jMyles 8y ago
See also the python (and reference) implementation, which OP has also worked on (and, disclaimer, I have too :-) ): https://github.com/nucypher/pyUmbral https://github.com/nucypher/pyUmbral
jitl 8y ago
What is “split-key threshold proxy re-encryption”? Can you give an example of the useful case here; what does this enable? I read the README and the blog post, and found neither contains a “wat is this”. The repo links to an Umbral paper PDF that’s hard to read on mobile - requiring a separate PDF viewer app with tiny font - which also doesn’t contain a concrete example in the abstract. ¯\_(ツ)_/¯ Maybe I’m not the target audience.
- tuxxy 8y ago
  We have a more feature-complete reference implementation of Umbral called pyUmbral you may want to look into[0]. We (NuCypher) are using this to build a blockchain privacy layer in the form of a decentralized key management system similar to AWS KMS or Google Cloud KMS. You can read our paper that describes our use-case here: https://www.nucypher.com/whitepapers/english.pdf https://www.nucypher.com/whitepapers/english.pdf 0. https://github.com/nucypher/pyUmbral https://github.com/nucypher/pyUmbral
- mwilkison 8y ago
  Proxy re-encryption (PRE) is a form of public key encryption that allows a semi-trusted proxy to transform ciphertext from being encrypted under one key to another, without learning anything about the underlying plaintext. A "re-encryption key" is used by the proxy to do this transformation. Umbral is a split-key version of PRE, which splits the re-encryption key into many shares. A threshold number of these shares are then required to re-encrypt the data (similar to Shamir’s Secret Sharing). Here's a post describing split-key threshold proxy re-encryption in slightly more detail: https://blog.nucypher.com/unveiling-umbral-3d9d4423cd71 https://blog.nucypher.com/unveiling-umbral-3d9d4423cd71
tptacek 8y ago
I don't understand why this is built on OpenSSL. I looked (not carefully! Very quickly!) and it looks like most of the cgo calls just hit OpenSSL's bignum interface. But Go already has a decent bignum interface, and for that matter curve implementations with rudiments sufficient to build additional curve support. A Go crypto library with an OpenSSL dependency is somewhat un-idiomatic. What does OpenSSL provide that Go doesn't have? I'm asking because I'm sure there's something (or you wouldn't have done this), and I'm curious.
- tuxxy 8y ago
  Go supports Bignums, this is true. I love Go's interfaces, but it doesn't support constant time arithmetic for all of the operations[0]. Go also doesn't support all the curves we need (mainly secp256k1). We also have a `Point` struct that hits the OpenSSL EC_POINT API. Go only supports constant time arithmetic for a few specific curves (also not secp256k1). 0. https://github.com/golang/go/issues/20654 https://github.com/golang/go/issues/20654

19 points by tuxxy 8y ago

Hey, everyone! For some context, here's our blogpost about this pre-release. We're really excited to debut our cryptography arithmetic layer for Go. It's the first step to making our split-key threshold proxy re-encryption library available in Go. https://blog.nucypher.com/introducing-goumbral-ce979e616359 https://blog.nucypher.com/introducing-goumbral-ce979e616359

jMyles 8y ago

See also the python (and reference) implementation, which OP has also worked on (and, disclaimer, I have too :-) ): https://github.com/nucypher/pyUmbral https://github.com/nucypher/pyUmbral

jitl 8y ago

What is “split-key threshold proxy re-encryption”? Can you give an example of the useful case here; what does this enable? I read the README and the blog post, and found neither contains a “wat is this”. The repo links to an Umbral paper PDF that’s hard to read on mobile - requiring a separate PDF viewer app with tiny font - which also doesn’t contain a concrete example in the abstract. ¯\_(ツ)_/¯ Maybe I’m not the target audience.

tuxxy 8y ago
We have a more feature-complete reference implementation of Umbral called pyUmbral you may want to look into[0]. We (NuCypher) are using this to build a blockchain privacy layer in the form of a decentralized key management system similar to AWS KMS or Google Cloud KMS. You can read our paper that describes our use-case here: https://www.nucypher.com/whitepapers/english.pdf https://www.nucypher.com/whitepapers/english.pdf 0. https://github.com/nucypher/pyUmbral https://github.com/nucypher/pyUmbral
mwilkison 8y ago
Proxy re-encryption (PRE) is a form of public key encryption that allows a semi-trusted proxy to transform ciphertext from being encrypted under one key to another, without learning anything about the underlying plaintext. A "re-encryption key" is used by the proxy to do this transformation. Umbral is a split-key version of PRE, which splits the re-encryption key into many shares. A threshold number of these shares are then required to re-encrypt the data (similar to Shamir’s Secret Sharing). Here's a post describing split-key threshold proxy re-encryption in slightly more detail: https://blog.nucypher.com/unveiling-umbral-3d9d4423cd71 https://blog.nucypher.com/unveiling-umbral-3d9d4423cd71

tptacek 8y ago

I don't understand why this is built on OpenSSL. I looked (not carefully! Very quickly!) and it looks like most of the cgo calls just hit OpenSSL's bignum interface. But Go already has a decent bignum interface, and for that matter curve implementations with rudiments sufficient to build additional curve support. A Go crypto library with an OpenSSL dependency is somewhat un-idiomatic. What does OpenSSL provide that Go doesn't have? I'm asking because I'm sure there's something (or you wouldn't have done this), and I'm curious.

tuxxy 8y ago
Go supports Bignums, this is true. I love Go's interfaces, but it doesn't support constant time arithmetic for all of the operations[0]. Go also doesn't support all the curves we need (mainly secp256k1). We also have a `Point` struct that hits the OpenSSL EC_POINT API. Go only supports constant time arithmetic for a few specific curves (also not secp256k1). 0. https://github.com/golang/go/issues/20654 https://github.com/golang/go/issues/20654