web-demo: verify capability

4 files changed, 71 insertions, 6 deletions

diff --git a/examples/web-demo/index.html b/examples/web-demo/index.html
index 66b2650..62d9dd3 100644
--- a/examples/web-demo/index.html
+++ b/examples/web-demo/index.html
@@ -13,7 +13,7 @@
       <div id="notes">
         <p>This is a demo of ERIS - An Encoding for Robust Immutable Storage.</p>
 
-        <p>ERIS encodes any content into uniformly sized (4kB) encrypted blocks. The original content can only be decoded with the URN (which contains the encryption key). </p>
+        <p>ERIS encodes any content into uniformly sized (4kB) encrypted blocks. The original content can only be decoded with the read capability (an URN which contains the encryption key). </p>
 
       </div>
 
@@ -63,6 +63,9 @@
           </details>
           <br>
           <button id="controls-decode">← Decode</button>
+          <br>
+          <br>
+          <button id="controls-verify">Verify</button>
 
           <br>
           <pre id="controls-error"></pre>
@@ -73,8 +76,13 @@
           <h2>Encoded</h2>
 
           <h3>Read capability</h3>
+          <p>The read capability allows content to be read</p>
           <input id="encoded-eris-read-cap" type="url"></input>
 
+          <h3>Verification capability</h3>
+          <p>The verification capability allows all blocks to be verified for integrity, but does not allow the content to be read</p>
+          <input id="encoded-eris-verification-cap" type="url"></input>
+
           <div id="blocks">
             <h3>Blocks</h3>
             <div id="block-container">
diff --git a/examples/web-demo/src/index.js b/examples/web-demo/src/index.js
index 61815af..ea4db5f 100644
--- a/examples/web-demo/src/index.js
+++ b/examples/web-demo/src/index.js
@@ -91,11 +91,13 @@ async function main () {
 
   const controlsEncode = document.getElementById('controls-encode')
   const controlsDecode = document.getElementById('controls-decode')
+  const controlsVerify = document.getElementById('controls-verify')
   const controlsInputType = document.getElementById('controls-input-type')
   const controlsError = document.getElementById('controls-error')
   const controlsSuccess = document.getElementById('controls-success')
 
   const encodedErisReadCap = document.getElementById('encoded-eris-read-cap')
+  const encodedErisVerificationCap = document.getElementById('encoded-eris-verification-cap')
   const blockContainer = document.getElementById('block-container')
 
   // a ContentAddressableStorage based on a JavaScipt Map
@@ -186,6 +188,8 @@ async function main () {
     try {
       const urn = await encode()
       encodedErisReadCap.value = urn
+      const verifyUrn = await ERIS.deriveVerificationCapability(urn)
+      encodedErisVerificationCap.value = verifyUrn
       renderBlocks(cas)
       setSuccess('Encoded!')
     } catch (err) {
@@ -205,6 +209,17 @@ async function main () {
     }
   }
 
+  controlsVerify.onclick = async function (e) {
+    setSuccess('')
+    try {
+      const verificationCap = encodedErisVerificationCap.value
+      await ERIS.verify(verificationCap, cas)
+      setSuccess('Verification passed!')
+    } catch (err) {
+      setError(err)
+    }
+  }
+
   inputLoadSampleVocabulary.onclick = function (e) {
     inputTextarea.value = signify
     controlsInputType.value = 'text/turtle'
diff --git a/examples/web-demo/style.css b/examples/web-demo/style.css
index d91edcb..3bafd3e 100644
--- a/examples/web-demo/style.css
+++ b/examples/web-demo/style.css
@@ -32,6 +32,11 @@ textarea {
     text-align: center;
 }
 
+#controls button {
+    font-size: 18px;
+    font-family: monospace;
+}
+
 #controls-error {
     background-color: red;
     white-space: pre-wrap;
@@ -54,6 +59,10 @@ textarea {
     width: 90%;
 }
 
+#encoded-eris-verification-cap {
+    width: 90%;
+}
+
 #encoded-data {
     white-space: pre-wrap;
     max-width: 90%;
diff --git a/src/eris.js b/src/eris.js
index 6cfb877..e4ddaea 100644
--- a/src/eris.js
+++ b/src/eris.js
@@ -173,14 +173,14 @@ async function buildMerkleTree (input, verificationKey, cas) {
   return finalize(state, 0)
 }
 
-function makeReadCapability (level, rootReference, readKey) {
+function makeCapability(type, level, rootReference, readKey) {
   const cap = new Uint8Array(67)
 
   // Set version to 0
   cap.set([0], 0)
 
-  // Set type to 0 (for read capability)
-  cap.set([0], 1)
+  // Set type
+  cap.set([0], type)
 
   // Set level
   cap.set([level], 2)
@@ -241,7 +241,7 @@ async function put (content, cas = new NullContentAddressableStorage()) {
 
   const tree = await buildMerkleTree(paddedAndEncrypted, verificationKey, cas)
 
-  return makeReadCapability(tree.level, tree.rootReference, readKey)
+  return makeCapability(0, tree.level, tree.rootReference, readKey)
 }
 
 async function * decodeTree (cas, verificationKey, ref, nodeLevel, nodeCount) {
@@ -317,10 +317,43 @@ async function get (capability, cas) {
   return unpadded
 }
 
+async function verify (capability, cas) {
+  capability = decodeCapability(capability)
+
+  var verificationKey
+
+  if (capability.type !== 0) {
+    verificationKey = await crypto.derive_verification_key(capability.key)
+  } else {
+    verificationKey = capability.key
+  }
+
+  const blockGenerator = decodeTree(cas, verificationKey, capability.rootReference, capability.level, 0)
+
+  await concatBlocks(blockGenerator)
+
+  return true
+}
+
+async function deriveVerificationCapability (capability) {
+  capability = decodeCapability(capability)
+
+  if (capability.type !== 0) {
+    throw new Error('Not a read capability')
+  }
+
+  const verificationKey = await crypto.derive_verification_key(capability.key)
+  return makeCapability(1, capability.level, capability.rootReference, verificationKey)
+}
+
 module.exports = {
   ContentAddressableStorage: ContentAddressableStorage,
   NullContentAddressableStorage: NullContentAddressableStorage,
   MapContentAddressableStorage: MapContentAddressableStorage,
+
   put: put,
-  get: get
+  get: get,
+  verify: verify,
+
+  deriveVerificationCapability: deriveVerificationCapability
 }