diff --git a/extension/js/common/core/crypto/key.ts b/extension/js/common/core/crypto/key.ts
index 51bcddabfb7..b856789671b 100644
--- a/extension/js/common/core/crypto/key.ts
+++ b/extension/js/common/core/crypto/key.ts
@@ -492,20 +492,40 @@ export class KeyUtil {
   public static validateChecksum = (armoredText: string): boolean => {
     const lines = armoredText.split('\n').map(l => l.trim());
 
+    // Filter out known non-data lines
     const dataCandidates = lines.filter(line => line.length > 0 && !line.startsWith('-----') && !line.startsWith('Version:') && !line.startsWith('Comment:'));
 
+    // Find checksum line
     const checksumIndex = dataCandidates.findIndex(line => line.startsWith('='));
     if (checksumIndex === -1) return false;
 
     const checksumLine = dataCandidates[checksumIndex].slice(1);
     const dataLines = dataCandidates.slice(0, checksumIndex);
 
-    const providedBytes = atob(checksumLine);
+    // Decode checksum
+    let providedBytes: string;
+    try {
+      providedBytes = atob(checksumLine);
+    } catch {
+      return false;
+    }
     if (providedBytes.length !== 3) return false;
 
     const providedCRC = (providedBytes.charCodeAt(0) << 16) | (providedBytes.charCodeAt(1) << 8) | providedBytes.charCodeAt(2);
 
-    const rawData = atob(dataLines.join(''));
+    // Attempt to decode all data lines (some may not be base64)
+    const decodedChunks: string[] = [];
+    for (const line of dataLines) {
+      try {
+        decodedChunks.push(atob(line));
+      } catch {
+        // Not a valid base64 line, skip it
+      }
+    }
+
+    if (decodedChunks.length === 0) return false;
+
+    const rawData = decodedChunks.join('');
     const dataBytes = new Uint8Array([...rawData].map(c => c.charCodeAt(0)));
 
     return KeyUtil.crc24(dataBytes) === providedCRC;