From b473bcb1541ce14a859c2e949bb734d23ef62f0f Mon Sep 17 00:00:00 2001
From: LLFourn <lloyd.fourn@gmail.com>
Date: Sun, 22 Dec 2024 22:29:38 +1100
Subject: [PATCH] =?UTF-8?q?[=E2=9D=84]=20Add=20SharedKey::share=5Fimage?=
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---
 schnorr_fun/src/frost/shared_key.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/schnorr_fun/src/frost/shared_key.rs b/schnorr_fun/src/frost/shared_key.rs
index 7ebe9f80..c610f33e 100644
--- a/schnorr_fun/src/frost/shared_key.rs
+++ b/schnorr_fun/src/frost/shared_key.rs
@@ -174,6 +174,18 @@ impl<T: PointType, Z: ZeroChoice> SharedKey<T, Z> {
 
         Some(Self::from_inner(poly))
     }
+
+    /// Gets an image at any index for the shared key. This can't be used for much other than
+    /// checking whether `Point` is the correct share image at a certain index. This can be useful
+    /// when you load in a share backup and want to check that it's correct.
+    ///
+    /// To verify a signature share for certain share you should use [`verification_share`] (which
+    /// contains a share image).
+    ///
+    /// [`verification_share`]: Self::verification_share
+    pub fn share_image(&self, index: PartyIndex) -> Point<NonNormal, Public, Zero> {
+        poly::point::eval(&self.point_polynomial, index)
+    }
 }
 
 impl SharedKey<Normal> {