diff --git a/include/polarssl/rsa.h b/include/polarssl/rsa.h
index 295a2db..e7ee76a 100644
--- a/include/polarssl/rsa.h
+++ b/include/polarssl/rsa.h
@@ -192,7 +192,7 @@
  *
  * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
  */
-int rsa_check_pubkey( rsa_context *ctx );
+int rsa_check_pubkey( const rsa_context *ctx );
 
 /**
  * \brief          Check a private RSA key
@@ -201,7 +201,7 @@
  *
  * \return         0 if successful, or an POLARSSL_ERR_RSA_XXX error code
  */
-int rsa_check_privkey( rsa_context *ctx );
+int rsa_check_privkey( const rsa_context *ctx );
 
 /**
  * \brief          Do an RSA public key operation
@@ -220,7 +220,7 @@
  *                 enough (eg. 128 bytes if RSA-1024 is used).
  */
 int rsa_public( rsa_context *ctx,
-                unsigned char *input,
+                const unsigned char *input,
                 unsigned char *output );
 
 /**
@@ -236,7 +236,7 @@
  *                 enough (eg. 128 bytes if RSA-1024 is used).
  */
 int rsa_private( rsa_context *ctx,
-                 unsigned char *input,
+                 const unsigned char *input,
                  unsigned char *output );
 
 /**
@@ -255,7 +255,7 @@
  */
 int rsa_pkcs1_encrypt( rsa_context *ctx,
                        int mode, int  ilen,
-                       unsigned char *input,
+                       const unsigned char *input,
                        unsigned char *output );
 
 /**
@@ -276,7 +276,7 @@
  */
 int rsa_pkcs1_decrypt( rsa_context *ctx,
                        int mode, int *olen,
-                       unsigned char *input,
+                       const unsigned char *input,
                        unsigned char *output,
 		               int output_max_len );
 
@@ -300,7 +300,7 @@
                     int mode,
                     int hash_id,
                     int hashlen,
-                    unsigned char *hash,
+                    const unsigned char *hash,
                     unsigned char *sig );
 
 /**
@@ -323,7 +323,7 @@
                       int mode,
                       int hash_id,
                       int hashlen,
-                      unsigned char *hash,
+                      const unsigned char *hash,
                       unsigned char *sig );
 
 /**