diff --git a/include/libssh/priv.h b/include/libssh/priv.h
index 975925b4..22b836b4 100644
--- a/include/libssh/priv.h
+++ b/include/libssh/priv.h
@@ -515,7 +515,7 @@ void ssh_set_error(void *error, int code, const char *descr, ...) PRINTF_ATTRIBU
 /* in dh.c */
 /* DH key generation */
 void dh_generate_e(SSH_SESSION *session);
-void ssh_print_bignum(char *which,bignum num);
+void ssh_print_bignum(const char *which,bignum num);
 void dh_generate_x(SSH_SESSION *session);
 void dh_generate_y(SSH_SESSION *session);
 void dh_generate_f(SSH_SESSION *session);
@@ -574,15 +574,16 @@ char *ssh_find_matching(const char *in_d, const char *what_d);
 
 /* in keyfiles.c */
 
-PRIVATE_KEY  *_privatekey_from_file(void *session,char *filename,int type);
+PRIVATE_KEY *_privatekey_from_file(void *session, const char *filename,
+    int type);
 
 /* in keys.c */
 const char *ssh_type_to_char(int type);
-int ssh_type_from_name(char *name);
+int ssh_type_from_name(const char *name);
 
 PRIVATE_KEY *privatekey_make_dss(SSH_SESSION *session, BUFFER *buffer);
 PRIVATE_KEY *privatekey_make_rsa(SSH_SESSION *session, BUFFER *buffer,
-    char *type);
+    const char *type);
 PRIVATE_KEY *privatekey_from_string(SSH_SESSION *session, STRING *privkey_s);
 
 PUBLIC_KEY *publickey_make_dss(SSH_SESSION *session, BUFFER *buffer);
@@ -658,15 +659,15 @@ void crypto_free(CRYPTO *crypto);
 u32 ssh_crc32(char *buffer, int len);
 
 /* auth1.c */
-int ssh_userauth1_none(SSH_SESSION *session, char *username);
-int ssh_userauth1_offer_pubkey(SSH_SESSION *session, char *username,
+int ssh_userauth1_none(SSH_SESSION *session, const char *username);
+int ssh_userauth1_offer_pubkey(SSH_SESSION *session, const char *username,
         int type, STRING *pubkey);
-int ssh_userauth1_password(SSH_SESSION *session, char *username,
-        char *password);
+int ssh_userauth1_password(SSH_SESSION *session, const char *username,
+        const char *password);
 /* in misc.c */
 /* gets the user home dir. */
 char *ssh_get_user_home_dir(void);
-int ssh_file_readaccess_ok(char *file);
+int ssh_file_readaccess_ok(const char *file);
 
 /* macro for byte ordering */
 u64 ntohll(u64);
diff --git a/libssh/dh.c b/libssh/dh.c
index 0ef3c90e..24e7257e 100644
--- a/libssh/dh.c
+++ b/libssh/dh.c
@@ -128,7 +128,7 @@ void ssh_crypto_finalize(void){
 }
    
 /* prints the bignum on stderr */
-void ssh_print_bignum(char *which,bignum num){
+void ssh_print_bignum(const char *which,bignum num){
 #ifdef HAVE_LIBGCRYPT
     unsigned char *hex;
     bignum_bn2hex(num,&hex);
diff --git a/libssh/keyfiles.c b/libssh/keyfiles.c
index 73a8704a..22ead297 100644
--- a/libssh/keyfiles.c
+++ b/libssh/keyfiles.c
@@ -596,7 +596,8 @@ PRIVATE_KEY  *privatekey_from_file(SSH_SESSION *session, const char *filename,
 }
 
 /* same that privatekey_from_file() but without any passphrase things. */
-PRIVATE_KEY  *_privatekey_from_file(void *session,char *filename,int type){
+PRIVATE_KEY *_privatekey_from_file(void *session, const char *filename,
+    int type) {
     FILE *file=fopen(filename,"r");
     PRIVATE_KEY *privkey;
 #ifdef HAVE_LIBGCRYPT
diff --git a/libssh/keys.c b/libssh/keys.c
index b1a9cc00..f7cf8e77 100644
--- a/libssh/keys.c
+++ b/libssh/keys.c
@@ -48,7 +48,7 @@ const char *ssh_type_to_char(int type) {
     }
 }
 
-int ssh_type_from_name(char *name) {
+int ssh_type_from_name(const char *name) {
   if (strcmp(name, "rsa1") == 0) {
     return TYPE_RSA1;
   } else if (strcmp(name, "rsa") == 0) {
diff --git a/libssh/misc.c b/libssh/misc.c
index c619530a..3f404fd2 100644
--- a/libssh/misc.c
+++ b/libssh/misc.c
@@ -95,7 +95,7 @@ char *ssh_get_user_home_dir(void) {
 #endif
 
 /* we have read access on file */
-int ssh_file_readaccess_ok(char *file){
+int ssh_file_readaccess_ok(const char *file){
     if(!access(file,R_OK))
         return 1;
     return 0;