diff --git a/src/dnssec-crypto.h b/src/dnssec-crypto.h
index 3591556..c89dd25 100644
--- a/src/dnssec-crypto.h
+++ b/src/dnssec-crypto.h
@@ -45,5 +45,6 @@ struct VerifyAlgCtx
 int verifyalg_supported(int algo);
 VerifyAlgCtx* verifyalg_alloc(int algo);
 void verifyalg_free(VerifyAlgCtx *a);
+int verifyalg_algonum(VerifyAlgCtx *a);
 
 #endif /* DNSSEC_CRYPTO_H */
diff --git a/src/dnssec-openssl.c b/src/dnssec-openssl.c
index 5cf2c41..3151cdb 100644
--- a/src/dnssec-openssl.c
+++ b/src/dnssec-openssl.c
@@ -201,3 +201,11 @@ void verifyalg_free(VerifyAlgCtx *a)
 
   pool_used &= ~(1 << pool_idx);
 }
+
+int verifyalg_algonum(VerifyAlgCtx *a)
+{
+  int num = a->vtbl - valgs;
+  if (num < 0 || num >= countof(valgs))
+    return -1;
+  return num;
+}