Warn when using weak entropy and strong mnemonic

2 files changed, 17 insertions, 0 deletions

diff --git a/src/index.html b/src/index.html
index df5bf67..4056610 100644
--- a/src/index.html
+++ b/src/index.html
@@ -113,6 +113,11 @@
                                             <option value="21">21 <span>Words</span></option>
                                             <option value="24">24 <span>Words</span></option>
                                         </select>
+                                        <p class="weak-entropy-override-warning hidden">
+                                            <span class="text-danger">
+                                                The mnemonic will appear more secure than it really is.
+                                            </span>
+                                        </p>
                                     </div>
                                 </div>
                                 <div class="col-sm-3">
diff --git a/src/js/index.js b/src/js/index.js
index 0a2d362..e96f4a9 100644
--- a/src/js/index.js
+++ b/src/js/index.js
@@ -40,6 +40,7 @@
     DOM.entropyWordIndexes = DOM.entropyContainer.find(".word-indexes");
     DOM.entropyChecksum = DOM.entropyContainer.find(".checksum");
     DOM.entropyMnemonicLength = DOM.entropyContainer.find(".mnemonic-length");
+    DOM.entropyWeakEntropyOverrideWarning = DOM.entropyContainer.find(".weak-entropy-override-warning");
     DOM.entropyFilterWarning = DOM.entropyContainer.find(".filter-warning");
     DOM.phrase = $(".phrase");
     DOM.passphrase = $(".passphrase");
@@ -1190,6 +1191,17 @@
             mnemonicLength = parseInt(mnemonicLength);
             var numberOfBits = 32 * mnemonicLength / 3;
             bits = bits.substring(0, numberOfBits);
+            // show warning for weak entropy override
+            if (mnemonicLength / 3 * 32 > entropy.binaryStr.length) {
+                DOM.entropyWeakEntropyOverrideWarning.removeClass("hidden");
+            }
+            else {
+                DOM.entropyWeakEntropyOverrideWarning.addClass("hidden");
+            }
+        }
+        else {
+            // hide warning for weak entropy override
+            DOM.entropyWeakEntropyOverrideWarning.addClass("hidden");
         }
         // Discard trailing entropy
         var bitsToUse = Math.floor(bits.length / 32) * 32;