Use uint64_t and avoid down casting as much as possible.

firmware/lib/cryptolib/include/rsa.h

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef VBOOT_REFERENCE_RSA_H_
 #define VBOOT_REFERENCE_RSA_H_
 
 #ifndef VBOOT_REFERENCE_CRYPTOLIB_H_
 #error "Do not include this file directly. Use cryptolib.h instead."
@@ skipping 57 matching lines @@
                                 unsigned int algorithm);
 
 
 /* ----Some additional utility functions for RSA.---- */
 
 /* Returns the size of a pre-processed RSA public key in
  * [out_size] with the algorithm [algorithm].
  *
  * Returns 1 on success, 0 on failure.
  */
-int RSAProcessedKeySize(unsigned int algorithm, int* out_size);
+uint64_t RSAProcessedKeySize(uint64_t algorithm, uint64_t* out_size);
 
 /* Allocate a new RSAPublicKey structure and initialize its pointer fields to
  * NULL */
 RSAPublicKey* RSAPublicKeyNew(void);
 
 /* Deep free the contents of [key]. */
 void RSAPublicKeyFree(RSAPublicKey* key);
 
 /* Create a RSAPublic key structure from binary blob [buf] of length
  * [len].
  *
  * Caller owns the returned key and must free it.
  */
-RSAPublicKey* RSAPublicKeyFromBuf(const uint8_t* buf, int len);
+RSAPublicKey* RSAPublicKeyFromBuf(const uint8_t* buf, uint64_t len);
 
 
 #endif  /* VBOOT_REFERENCE_RSA_H_ */