Implement Simple API to PRE and add UmbralDEM class #29

tuxxy · 2018-01-23T11:45:18Z

What this does:

Implements a simple API with the following methods:
- encrypt -- Encrypts data using KEM/DEM.
- decrypt -- Decrypts data using KEM/DEM.
- decrypt_reencrypted -- Decrypts threshold encrypted data using KEM/DEM.
- reencrypt -- Already in the PRE class.
- split_rekey -- Already in the PRE class. NOTE: Returns vKeys, disregard this for the time being via _ operator.
- reconstruct -- Already in the Capsule class. It is required to use the above methods; therefore is exposed in a similar fashion already.
Modifies input of the split_rekey method to allow for UmbralPrivateKey and UmbralPublicKey use.
Adds gen_key method to UmbralPrivateKey.
- Adds method get_pub_key to UmbralPrivateKey to calculate public key for the private key.
Privatizes the following methods in PRE:
- _encapsulate
- _decapsulate_reencrypted
Adds UmbralDEM:
- Handles symmetric encryption using NaCl's Salsa20-Poly1305.
  - Maybe switch to a cipher that allows authenticated data? This needs to be scoped/researched.
- Left to the user to read data from filesystem.
Fixes a circular import with UmbralParameters.
Adds tests for all these things.

@cygnusv and I had a call around 02:00MST/01:00PST and discussed the needs for the UmbralDEM class as well as the simple API implemented here.

The simple API is implemented in the core Umbral class PRE. Subpaths need to be handled on the KMS side. This does not implement or use any challenge methods.

NOTE: This merges to the `kms-depend` branch. After merging this branch, continue to merge to the `master` branch.

Good night.

Actually return key

Had a call with David, we discussed how we're implemting the needed API changes. We're going to use Umbral for Michael's API request. This DEM will be kept simple and simply use NaCl Salsa20-Poly1305 SecretBox. Add KEYSIZE attr on UmbralDEM

cygnusv · 2018-01-23T14:08:38Z

tests/test_umbral.py

+
+    priv_key = keys.UmbralPrivateKey.gen_key(params)
+    pub_key = priv_key.get_pub_key(params)
+


Perhaps change priv_key to priv_key_alice. The same for pub_key.

cygnusv

I think this is a leap forward to the target API discussed a couple of months ago. There are of course certain aspects that could be changed (e.g., do we want PRE to be a class or a module?), but I really think we can live with this as-is.

cygnusv · 2018-01-23T14:08:59Z

tests/test_umbral.py

+        priv_key_bob, pub_key_bob, pub_key, capsule, enc_data
+    )
+    assert reenc_dec_data == plain_data
+


Great, this is completely in line with Michael's API.

cygnusv · 2018-01-23T14:11:51Z

umbral/umbral.py

+
+        Returns the plaintext of the data.
+        """
+        # TODO: Do we take only the recipient's private key and form pubkey?


Yes, we can do that, since the public key can be deterministically derived from the private key.

…t_reencrypted

jMyles · 2018-01-24T00:05:11Z

tests/test_umbral.py

+@pytest.mark.parametrize("N,threshold", parameters)
+def test_simple_api(N, threshold):
+    params = umbral.UmbralParameters()
+    pre = umbral.PRE(params)


Just getting going on a more thorough review. Overall, this is a huge improvement from 24 hours ago!

I'll make Issues for things that are, at least to me, outstanding. I started on this line, with #31.

michwill · 2018-01-24T02:13:10Z

tests/test_umbral.py

+    rekeys, _ = pre.split_rekey(priv_key_alice, pub_key_bob, threshold, N)
+    for rekey in rekeys:
+        cFrag = pre.reencrypt(rekey, capsule)
+        capsule.attach_cfrag(cFrag)


Ah interesting. So we attach cFrag to exactly the original capsule, not a brand new one?

You attach it, then call capsule.reconstruct which returns a new capsule.

michwill

Simple, but powerful. Awesome first step to make a simple API

jMyles · 2018-01-24T02:23:24Z

tests/test_umbral.py

+    pub_key_bob = priv_key_bob.get_pub_key(params)
+
+    plain_data = b'attack at dawn'
+    enc_data, capsule = pre.encrypt(pub_key_alice, plain_data)


So, we really don't want to allow the user to optionally use their own symmetric tooling here? I think this is a big decision decision to be made without discussion.

Although, maybe it makes sense to do it this way for now and add the option later if we want?

I think, this can eventually be handled by having a default dem as a class attribute (well, at least on the basic level).
E.g.: dem = UmbralDEM(...) ->

class PRE(object): ... DEM = UmbralDEM

... dem = PRE.DEM(...)

It would probably be for the best, currently, if the user can't easily extend their own DEM. Umbral is defined to use Salsa20-Poly1305, but we'll be switching to ChaCha20-Poly1305 to allow for us to add in authenticated data for more security in the overall system.

For that reason, users really shouldn't try to roll their own crypto here. Though, they are free to write their own DEM if they like.

@cygnusv can elaborate on this more. We have an issue open for this as #30.

Well yeah, I think this adds +1 to having cls.DEM, but will wait on @jMyles opinion

I prefer for (in fact, I think that it only makes sense for) PRE to be a module, not a class. So maybe instead we have:

pre.set_dem_interface(MyCustomDEMClass)

We really need the KMS to have one standard DEM method. There isn't any good reason to have to make anything more complex when we have figured the one great way to do it.

@tuxxy: Oh yeah, I think we all agree there. I think this concern is more about making sure we have flexibility to build things other than the KMS.

The way you've written this, I think we can probably just add an additional interface later without too much trouble. So I think we can actually just move with this as-is.

jMyles · 2018-01-24T02:26:30Z

tests/test_umbral.py

@@ -84,7 +113,7 @@ def test_cfrag_serialization():
    priv_key = pre.gen_priv()
    pub_key = pre.priv2pub(priv_key)

-    _, capsule = pre.encapsulate(pub_key)
+    _, capsule = pre._encapsulate(pub_key)


I don't really like _ as a name in tests - do you think it makes sense to just call this _key_bytes?

jMyles · 2018-01-24T02:28:09Z

tests/test_umbral.py

@@ -84,7 +113,7 @@ def test_cfrag_serialization():
    priv_key = pre.gen_priv()
    pub_key = pre.priv2pub(priv_key)

-    _, capsule = pre.encapsulate(pub_key)
+    _, capsule = pre._encapsulate(pub_key)
    kfrags, _ = pre.split_rekey(priv_key, pub_key, 1, 2)


Same here - maybe call this _verification_keys.

jMyles

Huge step in a great direction.

Add more unused variables

Merge #29 into master

tuxxy added 6 commits January 23, 2018 00:33

Add gen_key classmethods to UmbralPrivateKey and UmbralPublicKey

8cce181

Actually return key

Add tests for checking generated keys

00c5089

Add skeleton of DEM

3a8f4c8

Use basic DEM principles

74f989e

Had a call with David, we discussed how we're implemting the needed API changes. We're going to use Umbral for Michael's API request. This DEM will be kept simple and simply use NaCl Salsa20-Poly1305 SecretBox. Add KEYSIZE attr on UmbralDEM

Add simple API

250cf3c

Add tests and fix a few things

3eafb28

tuxxy requested review from cygnusv, jMyles and michwill January 23, 2018 11:46

cygnusv reviewed Jan 23, 2018

View reviewed changes

cygnusv approved these changes Jan 23, 2018

View reviewed changes

cygnusv mentioned this pull request Jan 23, 2018

Use cryptography.io's AEAD in UmbralDEM #30

Closed

tuxxy added 2 commits January 23, 2018 13:46

Use priv/pub_key_alice in test

4974686

Calculate recipient public key from recipient's private key in decryp…

b1f04f7

…t_reencrypted

jMyles reviewed Jan 24, 2018

View reviewed changes

michwill reviewed Jan 24, 2018

View reviewed changes

michwill approved these changes Jan 24, 2018

View reviewed changes

jMyles reviewed Jan 24, 2018

View reviewed changes

jMyles approved these changes Jan 24, 2018

View reviewed changes

Name unused variables

f7687d0

Add more unused variables

tuxxy force-pushed the kms-depend branch from bf51b22 to f7687d0 Compare January 24, 2018 03:00

tuxxy merged commit 21c0a32 into nucypher:kms-depend Jan 24, 2018

tuxxy mentioned this pull request Jan 24, 2018

Merge #29 into master #32

Merged

tuxxy added a commit that referenced this pull request Jan 24, 2018

Merge pull request #32 from nucypher/kms-depend

d91b0bf

Merge #29 into master

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Implement Simple API to PRE and add UmbralDEM class #29

Implement Simple API to PRE and add UmbralDEM class #29

tuxxy commented Jan 23, 2018 •

edited

Loading

cygnusv Jan 23, 2018

cygnusv left a comment

cygnusv Jan 23, 2018

cygnusv Jan 23, 2018

jMyles Jan 24, 2018

michwill Jan 24, 2018

tuxxy Jan 24, 2018

michwill left a comment

jMyles Jan 24, 2018

michwill Jan 24, 2018

tuxxy Jan 24, 2018 •

edited

Loading

michwill Jan 24, 2018

jMyles Jan 24, 2018

tuxxy Jan 24, 2018

jMyles Jan 24, 2018

jMyles Jan 24, 2018

jMyles Jan 24, 2018

jMyles left a comment


		priv_key = keys.UmbralPrivateKey.gen_key(params)
		pub_key = priv_key.get_pub_key(params)

Implement Simple API to PRE and add UmbralDEM class #29

Implement Simple API to PRE and add UmbralDEM class #29

Conversation

tuxxy commented Jan 23, 2018 • edited Loading

What this does:

NOTE: This merges to the kms-depend branch. After merging this branch, continue to merge to the master branch.

Choose a reason for hiding this comment

cygnusv left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

michwill left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

tuxxy Jan 24, 2018 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

jMyles left a comment

Choose a reason for hiding this comment

tuxxy commented Jan 23, 2018 •

edited

Loading

NOTE: This merges to the `kms-depend` branch. After merging this branch, continue to merge to the `master` branch.

tuxxy Jan 24, 2018 •

edited

Loading