From f83a99b82300ad1fcb77bb26633214649d1d871e Mon Sep 17 00:00:00 2001
From: Aditya Belsare <asbel@google.com>
Date: Mon, 7 Jul 2025 12:01:17 -0700
Subject: [PATCH] Add a method to export the public key as a BigInteger

---
 src/com/google/cose/OkpKey.java | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/com/google/cose/OkpKey.java b/src/com/google/cose/OkpKey.java
index 58552f1..c39ece1 100644
--- a/src/com/google/cose/OkpKey.java
+++ b/src/com/google/cose/OkpKey.java
@@ -9,6 +9,7 @@
 import com.google.cose.exceptions.CoseException;
 import com.google.cose.utils.CborUtils;
 import com.google.cose.utils.Headers;
+import java.math.BigInteger;
 import java.util.Arrays;
 
 /**
@@ -41,6 +42,15 @@ public byte[] getPublicKeyBytes() {
     return Arrays.copyOf(publicKeyBytes, publicKeyBytes.length);
   }
 
+  public BigInteger getPublicKeyBytesAsBigInteger() {
+    // Reverse the bytes to get the correct big-endian representation.
+    byte[] reversedBytes = new byte[publicKeyBytes.length];
+    for (int i = 0; i < publicKeyBytes.length; i++) {
+      reversedBytes[i] = publicKeyBytes[publicKeyBytes.length - 1 - i];
+    }
+    return new BigInteger(1, reversedBytes);
+  }
+  
   /** Recursive builder to build out the Ec2 key and its subclasses. */
   abstract static class Builder<T extends Builder<T>> extends CoseKey.Builder<T> {
     private Integer curve = null;