librustzcash APIs for wallet key manipulation #9

arcalinea · 2018-05-14T12:01:18Z

librustzcash_to_scalar
librustzcash_ask_to_ak
librustzcash_nsk_to_nk
librustzcash_crh_ivk
librustzcash_check_diversifier
librustzcash_ivk_to_pkd

ebfull · 2018-05-14T22:17:05Z

Can you rebase this on top of the latest librustzcash?

arcalinea · 2018-05-14T23:37:34Z

Rebased

ebfull · 2018-05-15T08:36:05Z

src/rustzcash.rs

+}
+
+#[no_mangle]
+pub extern "system" fn librustzcash_crh_ivk(


Psst! There's an API for this in sapling-crypto.

https://github.com/zcash-hackworks/sapling-crypto/blob/master/src/primitives/mod.rs#L89

I can see why you might not want to use it though. It looks like you do the right thing here, so meh, it's okay.

Well, kinda. I think you should do what my code does, interpret it as a scalar (it should always work) and then use a write_fs afterwards, which should be implemented to write out in little endian bit order.

Using that API requires six additional conversion read/write operations (to convert ak and nk to scalars and back, and to convert ivk to a Point and back). It didn't seem worth the cycles.

Once this has been rebased, we should test this function against the test vectors.

ebfull · 2018-05-15T08:38:51Z

src/rustzcash.rs

+
+    let result = unsafe { &mut *result };
+
+    scalar.as_mut().reverse();


We should be doing some kind of write_fs here instead.

So extract it into a separate function like we did for read_fs?

I tried this in latest commit

ebfull · 2018-05-15T08:46:41Z

src/rustzcash.rs

+/// Reads an FsRepr from [u8] of length 32
+/// This will panic (abort) if length provided is
+/// not correct
+fn read_fs(from: &[u8]) -> FsRepr {


This will read from bytes into an Fs in little-endian bit order, which is what we want, but the function librustzcash_crh_ivk produces a little-endian byte order result and writes that out. Then, when you call librustzcash_ivk_to_pkd, it's not going to work correctly.

Does it? I thought the intention was that the output of BLAKE2s was exactly the representation we wanted. More precisely, I think this is fine, because:

Here we are reading a little-endian byte array in big-endian, and then flipping, which means we need to flip both the u64s and their bits.

In ViewingKey.ivk() we flip the little-endian byte array before reading it as big endian, and since the endianness of the bits within each byte doesn't matter for reading, that should mean the result is the same as we get here by flipping the bits above.

I'll try and generate some test vectors to confirm.

Now that #12 has been merged, this function needs to be updated (to use read_le and not swap bits).

str4d

All new APIs should be tested against the test vectors that are now in master.

str4d · 2018-05-22T23:45:52Z

src/rustzcash.rs

+/// Reads an FsRepr from [u8] of length 32
+/// This will panic (abort) if length provided is
+/// not correct
+fn read_fs(from: &[u8]) -> FsRepr {


Now that #12 has been merged, this function needs to be updated (to use read_le and not swap bits).

str4d · 2018-05-22T23:46:02Z

src/rustzcash.rs

+        *b = swap_bits_u64(*b);
+    }
+
+    f.write_be(to).expect("length is 32 bytes");


Now that #12 has been merged, this function needs to be updated (to use read_le and not swap bits).

str4d · 2018-05-22T23:48:37Z

src/rustzcash.rs

+}
+
+#[no_mangle]
+pub extern "system" fn librustzcash_crh_ivk(


Once this has been rebased, we should test this function against the test vectors.

str4d

Also needs tests (calling these functions inside the key component test function, and checking the output, should suffice).

str4d · 2018-05-25T02:08:16Z

src/rustzcash.rs

+    let mut f = <<Bls12 as JubjubEngine>::Fs as PrimeField>::Repr::default();
+    f.read_le(from).expect("length is 32 bytes");
+
+    f.as_mut().reverse();


This needed to be removed as well.

str4d · 2018-05-25T02:09:37Z

src/rustzcash.rs

+fn write_fs(mut f: FsRepr, to: &mut [u8]) {
+    assert_eq!(to.len(), 32);
+
+    f.as_mut().reverse();


This needed to be removed as well.

Should the reverse() on line 80 also be removed?

str4d · 2018-05-30T23:30:18Z

I rebased this PR on master to fix merge conflicts and remove some stray commits that had crept in.

str4d

ACK+cov

str4d · 2018-05-30T23:34:16Z

src/rustzcash.rs

+) {
+    // Should be okay, because caller is responsible for ensuring
+    // the pointer is a valid pointer to 32 bytes, and that is the
+    // size of the representation


Comment is out-of-date (I think it might be intended to apply to the unsafe conversion of result).

Add Sapling key classes to wallet Leverages new librustzcash APIs added in zcash/librustzcash#9

Various improvements to project structure and implementation This makes wNAF/multiexp more modularized and abstract (for use later in remodeling groth) and starts moving other things around. Also, good chance to start working on buildbot.

arcalinea requested a review from str4d May 14, 2018 12:01

arcalinea force-pushed the wallet-apis branch from bff0c5e to b2ab9db Compare May 14, 2018 23:30

arcalinea force-pushed the wallet-apis branch 4 times, most recently from 77b724f to b184cc6 Compare May 15, 2018 03:49

str4d changed the title ~~WIP: Sapling to_scalar wallet API~~ librustzcash APIs for wallet key manipulation May 15, 2018

arcalinea force-pushed the wallet-apis branch 2 times, most recently from 115f152 to 06990af Compare May 15, 2018 06:00

ebfull requested changes May 15, 2018

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arcalinea mentioned this pull request May 15, 2018

Add Sapling key classes to wallet zcash/zcash#3269

Merged

str4d mentioned this pull request May 22, 2018

Add interface and computation of Sapling note commitment #11

Merged

str4d requested changes May 22, 2018

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arcalinea self-assigned this May 23, 2018

str4d requested changes May 25, 2018

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arcalinea force-pushed the wallet-apis branch from acad037 to 9b83436 Compare May 25, 2018 08:01

str4d force-pushed the wallet-apis branch from 1e1ef97 to dd1d302 Compare May 30, 2018 00:04

arcalinea force-pushed the wallet-apis branch from dd1d302 to 3026948 Compare May 30, 2018 15:43

Jay Graber and others added 5 commits May 31, 2018 11:05

Add to_scalar call

128af9f

Add ask_to_ak and nsk_to_nk

c44d702

Add crh_ivk

23c2f0e

Add check_diversifier and ivk_to_pkd

be1b307

Test librustzcash key component APIs against test vectors

b54e028

str4d force-pushed the wallet-apis branch from 3026948 to b54e028 Compare May 30, 2018 23:27

str4d approved these changes May 30, 2018

View reviewed changes

ebfull approved these changes May 31, 2018

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str4d merged commit 18f4945 into zcash:master May 31, 2018

zkbot added a commit to zcash/zcash that referenced this pull request Jun 5, 2018

Auto merge of #3269 - arcalinea:sapling_wallet_classes, r=ebfull

b4874e9

Add Sapling key classes to wallet Leverages new librustzcash APIs added in zcash/librustzcash#9

str4d referenced this pull request in str4d/librustzcash Aug 28, 2018

Ordering cleanup for Fq/Fq2, with documentation. Closes #9.

e726600

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librustzcash APIs for wallet key manipulation #9

librustzcash APIs for wallet key manipulation #9

arcalinea commented May 14, 2018 •

edited by str4d

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		let result = unsafe { &mut *result };

		scalar.as_mut().reverse();

librustzcash APIs for wallet key manipulation #9

librustzcash APIs for wallet key manipulation #9

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arcalinea commented May 14, 2018 • edited by str4d Loading

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arcalinea commented May 14, 2018 •

edited by str4d

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str4d May 16, 2018 •

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