diff --git a/android_keymaster.cpp b/android_keymaster.cpp
index 568cfa4..687a5ca 100644
--- a/android_keymaster.cpp
+++ b/android_keymaster.cpp
@@ -283,7 +283,7 @@
         return;
 
     operation->SetAuthorizations(key->authorizations());
-    response->error = operation_table_->Add(operation.release(), &response->op_handle);
+    response->error = operation_table_->Add(operation.release(), *context_, &response->op_handle);
 }
 
 void AndroidKeymaster::UpdateOperation(const UpdateOperationRequest& request,
diff --git a/ecdsa_keymaster1_operation.h b/ecdsa_keymaster1_operation.h
index 6045686..2066639 100644
--- a/ecdsa_keymaster1_operation.h
+++ b/ecdsa_keymaster1_operation.h
@@ -43,7 +43,9 @@
 
     keymaster_error_t GetError(EVP_PKEY* ecdsa_key);
 
-  protected:
+    keymaster_operation_handle_t GetOperationHandle() const { return operation_handle_; }
+
+  private:
     keymaster_purpose_t purpose_;
     keymaster_operation_handle_t operation_handle_;
     const Keymaster1Engine* engine_;
@@ -90,6 +92,12 @@
         return super::Abort();
     }
 
+    keymaster_error_t CreateOperationHandle(const KeymasterContext& /* context */,
+                                            keymaster_operation_handle_t* op_handle) override {
+        *op_handle = wrapped_operation_.GetOperationHandle();
+        return KM_ERROR_OK;
+    }
+
   private:
     EcdsaKeymaster1WrappedOperation wrapped_operation_;
 };
diff --git a/openssl_err.cpp b/openssl_err.cpp
index 078b8e3..d8398bd 100644
--- a/openssl_err.cpp
+++ b/openssl_err.cpp
@@ -167,6 +167,7 @@
     case RSA_R_DATA_TOO_SMALL_FOR_KEY_SIZE:
         return KM_ERROR_INVALID_INPUT_LENGTH;
     case RSA_R_DATA_TOO_LARGE_FOR_MODULUS:
+    case RSA_R_DATA_TOO_LARGE:
         return KM_ERROR_INVALID_ARGUMENT;
     default:
         return KM_ERROR_UNKNOWN_ERROR;
diff --git a/operation.cpp b/operation.cpp
index 410c9aa..cb46b45 100644
--- a/operation.cpp
+++ b/operation.cpp
@@ -17,6 +17,7 @@
 #include "operation.h"
 
 #include <keymaster/authorization_set.h>
+#include <keymaster/keymaster_context.h>
 
 #include "key.h"
 
@@ -134,6 +135,11 @@
     return true;
 }
 
+keymaster_error_t Operation::CreateOperationHandle(const KeymasterContext& context,
+                                                   keymaster_operation_handle_t* op_handle) {
+    return context.GenerateRandom(reinterpret_cast<uint8_t*>(op_handle), sizeof(*op_handle));
+}
+
 keymaster_error_t Operation::UpdateForFinish(const AuthorizationSet& input_params,
                                              const Buffer& input) {
     if (!input_params.empty() || input.available_read()) {
diff --git a/operation.h b/operation.h
index aadc406..1415f04 100644
--- a/operation.h
+++ b/operation.h
@@ -30,6 +30,7 @@
 
 class AuthorizationSet;
 class Key;
+class KeymasterContext;
 class Operation;
 
 class OperationFactory {
@@ -109,8 +110,10 @@
                                      const Buffer& signature, AuthorizationSet* output_params,
                                      Buffer* output) = 0;
     virtual keymaster_error_t Abort() = 0;
+    virtual keymaster_error_t CreateOperationHandle(const KeymasterContext& context,
+                                                    keymaster_operation_handle_t* op_handle);
 
-protected:
+  protected:
     // Helper function for implementing Finish() methods that need to call Update() to process
     // input, but don't expect any output.
     keymaster_error_t UpdateForFinish(const AuthorizationSet& input_params, const Buffer& input);
diff --git a/operation_table.cpp b/operation_table.cpp
index 533f754..cf907c8 100644
--- a/operation_table.cpp
+++ b/operation_table.cpp
@@ -31,7 +31,7 @@
     handle = 0;
 }
 
-keymaster_error_t OperationTable::Add(Operation* operation,
+keymaster_error_t OperationTable::Add(Operation* operation, const KeymasterContext& context,
                                       keymaster_operation_handle_t* op_handle) {
     if (!table_.get()) {
         table_.reset(new (std::nothrow) Entry[table_size_]);
@@ -40,8 +40,9 @@
     }
 
     UniquePtr<Operation> op(operation);
-    if (RAND_bytes(reinterpret_cast<uint8_t*>(op_handle), sizeof(*op_handle)) != 1)
-        return TranslateLastOpenSslError();
+    keymaster_error_t error = operation->CreateOperationHandle(context, op_handle);
+    if (error != KM_ERROR_OK)
+        return error;
     if (*op_handle == 0) {
         // Statistically this is vanishingly unlikely, which means if it ever happens in practice,
         // it indicates a broken RNG.
diff --git a/operation_table.h b/operation_table.h
index 0f3f096..3ac8506 100644
--- a/operation_table.h
+++ b/operation_table.h
@@ -23,6 +23,7 @@
 
 namespace keymaster {
 
+class KeymasterContext;
 class Operation;
 
 class OperationTable {
@@ -39,7 +40,8 @@
         Operation* operation;
     };
 
-    keymaster_error_t Add(Operation* operation, keymaster_operation_handle_t* op_handle);
+    keymaster_error_t Add(Operation* operation, const KeymasterContext& context,
+                          keymaster_operation_handle_t* op_handle);
     Operation* Find(keymaster_operation_handle_t op_handle);
     bool Delete(keymaster_operation_handle_t);
 
diff --git a/rsa_keymaster1_operation.h b/rsa_keymaster1_operation.h
index 30123f0..1cfa8be 100644
--- a/rsa_keymaster1_operation.h
+++ b/rsa_keymaster1_operation.h
@@ -43,7 +43,9 @@
 
     keymaster_error_t GetError(EVP_PKEY* rsa_key);
 
-  protected:
+    keymaster_operation_handle_t GetOperationHandle() const { return operation_handle_; }
+
+  private:
     keymaster_purpose_t purpose_;
     keymaster_operation_handle_t operation_handle_;
     const Keymaster1Engine* engine_;
@@ -90,6 +92,12 @@
         return super::Abort();
     }
 
+    keymaster_error_t CreateOperationHandle(const KeymasterContext& /* context */,
+                                            keymaster_operation_handle_t* op_handle) override {
+        *op_handle = wrapped_operation_.GetOperationHandle();
+        return KM_ERROR_OK;
+    }
+
   private:
     RsaKeymaster1WrappedOperation wrapped_operation_;
 };