Add function to calculate the required size of the buffer for public …

…signals.
iden3 · Feb 1, 2024 · 1829c1e · 1829c1e
1 parent ea72e69
commit 1829c1e
Show file tree

Hide file tree

Showing 2 changed files with 47 additions and 0 deletions.
diff --git a/src/prover.cpp b/src/prover.cpp
@@ -65,6 +65,29 @@ unsigned long CalcPublicBufferSize(const void *zkey_buffer, unsigned long zkey_s
     return 0;
 }
 
+int
+groth16_public_size_for_zkey_file(const char *zkey_fname,
+                                  unsigned   long *public_size,
+                                  char       *error_msg,        unsigned long  error_msg_maxsize) {
+    try {
+        auto zkey = BinFileUtils::openExisting(zkey_fname, "zkey", 1);
+        auto zkeyHeader = ZKeyUtils::loadHeader(zkey.get());
+        *public_size = PublicBufferMinSize(zkeyHeader->nPublic);
+    } catch (std::exception& e) {
+        if (error_msg) {
+            strncpy(error_msg, e.what(), error_msg_maxsize);
+        }
+        return PROVER_ERROR;
+    } catch (...) {
+        if (error_msg) {
+            strncpy(error_msg, "unknown error", error_msg_maxsize);
+        }
+        return PROVER_ERROR;
+    }
+
+    return 0;
+}
+
 int
 groth16_prover(const void *zkey_buffer,   unsigned long  zkey_size,
                const void *wtns_buffer,   unsigned long  wtns_size,
@@ -91,6 +114,16 @@ groth16_prover(const void *zkey_buffer,   unsigned long  zkey_size,
 
         if (*proof_size < proofMinSize || *public_size < publicMinSize) {
 
+            if (*proof_size < proofMinSize) {
+                snprintf(error_msg, error_msg_maxsize,
+                         "Proof buffer is too short. Minimum size: %lu, actual size: %lu",
+                         proofMinSize, *proof_size);
+            } else {
+                snprintf(error_msg, error_msg_maxsize,
+                         "Public buffer is too short. Minimum size: %lu, actual size: %lu",
+                         publicMinSize, *public_size);
+            }
+
             *proof_size  = proofMinSize;
             *public_size = publicMinSize;
 

diff --git a/src/prover.h b/src/prover.h
@@ -17,6 +17,20 @@ extern "C" {
  */
 unsigned long CalcPublicBufferSize(const void *zkey_buffer, unsigned long zkey_size);
 
+/**
+ * groth16_public_size_for_zkey_file calculates minimum buffer size for
+ * JSON-formatted public signals. The calculated buffer size is written
+ * to the public_size variable.
+ *
+ * @return error code:
+ *        PROVER_OK (0) - in case of success
+ *        PROVER_ERROR - in case of an error, error_msg contains the error message
+ */
+int
+groth16_public_size_for_zkey_file(const char *zkey_fname,
+                                  unsigned   long *public_size,
+                                  char       *error_msg,        unsigned long  error_msg_maxsize);
+
 /**
  * groth16_prover
  * @return error code: