Merge pull request #76 from BitGo/BG-16466.move-zcash-readwrite-to-bufferutils

refactor(zcash): move read/write to bufferutils

Author: Mark Erhardt

src/forks/zcash/bufferutils.js

@@ -1,13 +1,156 @@
-const { BufferReader } = require('../../bufferutils')
+const typeforce = require('typeforce')
+const types = require('../../types')
+const version = require('./version')
+
+const { BufferReader, BufferWriter } = require('../../bufferutils')
+
+const NUM_JOINSPLITS_INPUTS = 2
+const NUM_JOINSPLITS_OUTPUTS = 2
+const NOTECIPHERTEXT_SIZE = 1 + 8 + 32 + 32 + 512 + 16
+
+const G1_PREFIX_MASK = 0x02
+const G2_PREFIX_MASK = 0x0a
 
 class ZcashBufferReader extends BufferReader {
+  constructor (buffer, offset, txVersion) {
+    super(buffer, offset)
+    typeforce(types.maybe(types.Int32), txVersion)
+    this.txVersion = txVersion
+  }
+
   readInt64 () {
     const a = this.buffer.readUInt32LE(this.offset)
     let b = this.buffer.readInt32LE(this.offset + 4)
     b *= 0x100000000
     this.offset += 8
     return b + a
   }
+
+  readCompressedG1 () {
+    var yLsb = this.readUInt8() & 1
+    var x = this.readSlice(32)
+    return {
+      x: x,
+      yLsb: yLsb
+    }
+  }
+
+  readCompressedG2 () {
+    var yLsb = this.readUInt8() & 1
+    var x = this.readSlice(64)
+    return {
+      x: x,
+      yLsb: yLsb
+    }
+  }
+
+  readZKProof () {
+    var zkproof
+    if (this.txVersion >= version.SAPLING) {
+      zkproof = {
+        sA: this.readSlice(48),
+        sB: this.readSlice(96),
+        sC: this.readSlice(48)
+      }
+    } else {
+      zkproof = {
+        gA: this.readCompressedG1(),
+        gAPrime: this.readCompressedG1(),
+        gB: this.readCompressedG2(),
+        gBPrime: this.readCompressedG1(),
+        gC: this.readCompressedG1(),
+        gCPrime: this.readCompressedG1(),
+        gK: this.readCompressedG1(),
+        gH: this.readCompressedG1()
+      }
+    }
+    return zkproof
+  }
+
+  readJoinSplit () {
+    var vpubOld = this.readUInt64()
+    var vpubNew = this.readUInt64()
+    var anchor = this.readSlice(32)
+    var nullifiers = []
+    for (var j = 0; j < NUM_JOINSPLITS_INPUTS; j++) {
+      nullifiers.push(this.readSlice(32))
+    }
+    var commitments = []
+    for (j = 0; j < NUM_JOINSPLITS_OUTPUTS; j++) {
+      commitments.push(this.readSlice(32))
+    }
+    var ephemeralKey = this.readSlice(32)
+    var randomSeed = this.readSlice(32)
+    var macs = []
+    for (j = 0; j < NUM_JOINSPLITS_INPUTS; j++) {
+      macs.push(this.readSlice(32))
+    }
+
+    var zkproof = this.readZKProof()
+    var ciphertexts = []
+    for (j = 0; j < NUM_JOINSPLITS_OUTPUTS; j++) {
+      ciphertexts.push(this.readSlice(NOTECIPHERTEXT_SIZE))
+    }
+    return {
+      vpubOld: vpubOld,
+      vpubNew: vpubNew,
+      anchor: anchor,
+      nullifiers: nullifiers,
+      commitments: commitments,
+      ephemeralKey: ephemeralKey,
+      randomSeed: randomSeed,
+      macs: macs,
+      zkproof: zkproof,
+      ciphertexts: ciphertexts
+    }
+  }
+
+  readShieldedSpend () {
+    var cv = this.readSlice(32)
+    var anchor = this.readSlice(32)
+    var nullifier = this.readSlice(32)
+    var rk = this.readSlice(32)
+    var zkproof = this.readZKProof()
+    var spendAuthSig = this.readSlice(64)
+    return {
+      cv: cv,
+      anchor: anchor,
+      nullifier: nullifier,
+      rk: rk,
+      zkproof: zkproof,
+      spendAuthSig: spendAuthSig
+    }
+  }
+
+  readShieldedOutput () {
+    var cv = this.readSlice(32)
+    var cmu = this.readSlice(32)
+    var ephemeralKey = this.readSlice(32)
+    var encCiphertext = this.readSlice(580)
+    var outCiphertext = this.readSlice(80)
+    var zkproof = this.readZKProof()
+
+    return {
+      cv: cv,
+      cmu: cmu,
+      ephemeralKey: ephemeralKey,
+      encCiphertext: encCiphertext,
+      outCiphertext: outCiphertext,
+      zkproof: zkproof
+    }
+  }
+}
+
+class ZcashBufferWriter extends BufferWriter {
+  writeCompressedG1 (i) {
+    this.writeUInt8(G1_PREFIX_MASK | i.yLsb)
+    this.writeSlice(i.x)
+  }
+
+  writeCompressedG2 (i) {
+    this.writeUInt8(G2_PREFIX_MASK | i.yLsb)
+    this.writeSlice(i.x)
+  }
 }
 
-module.exports = { ZcashBufferReader }
+module.exports = { ZcashBufferReader, ZcashBufferWriter }

src/forks/zcash/version.js

@@ -0,0 +1,5 @@
+module.exports = {
+  JOINSPLITS_SUPPORT: 2,
+  OVERWINTER: 3,
+  SAPLING: 4
+}