diff --git a/lib/otp/otp.h b/lib/otp/otp.h
index 51847b550..51625a815 100644
--- a/lib/otp/otp.h
+++ b/lib/otp/otp.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 1996, 1997 Kungliga Tekniska Högskolan
+ * Copyright (c) 1995 - 2000 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden).
  * All rights reserved.
  * 
@@ -60,7 +60,7 @@ typedef struct {
   OtpAlgID id;
   char *name;
   int hashsize;
-  int (*hash)(char *s, size_t len, unsigned char *res);
+  int (*hash)(const char *s, size_t len, unsigned char *res);
   int (*init)(OtpKey key, char *pwd, char *seed);
   int (*next)(OtpKey key);
 } OtpAlgorithm;
@@ -82,13 +82,13 @@ void otp_print_hex (OtpKey key, char *str, size_t sz);
 void otp_print_stddict_extended (OtpKey key, char *str, size_t sz);
 void otp_print_hex_extended (OtpKey key, char *str, size_t sz);
 unsigned otp_checksum (OtpKey key);
-int otp_parse_hex (OtpKey key, char *);
-int otp_parse_stddict (OtpKey key, char *);
-int otp_parse_altdict (OtpKey key, char *, OtpAlgorithm *);
-int otp_parse (OtpKey key, char *, OtpAlgorithm *);
+int otp_parse_hex (OtpKey key, const char *);
+int otp_parse_stddict (OtpKey key, const char *);
+int otp_parse_altdict (OtpKey key, const char *, OtpAlgorithm *);
+int otp_parse (OtpKey key, const char *, OtpAlgorithm *);
 int otp_challenge (OtpContext *ctx, char *user, char *str, size_t len);
-int otp_verify_user (OtpContext *ctx, char *passwd);
-int otp_verify_user_1 (OtpContext *ctx, char *passwd);
+int otp_verify_user (OtpContext *ctx, const char *passwd);
+int otp_verify_user_1 (OtpContext *ctx, const char *passwd);
 char *otp_error (OtpContext *ctx);
 
 void *otp_db_open (void);
diff --git a/lib/otp/otp_parse.c b/lib/otp/otp_parse.c
index 9141776b4..6f4af9fd4 100644
--- a/lib/otp/otp_parse.c
+++ b/lib/otp/otp_parse.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 1996, 1997, 1998, 1999 Kungliga Tekniska Högskolan
+ * Copyright (c) 1995 - 2000 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden).
  * All rights reserved.
  * 
@@ -56,11 +56,11 @@ cmp(const void *a, const void *b)
 }
 
 static int
-get_stdword (char *s, void *v)
+get_stdword (const char *s, void *v)
 {
   struct e e, *r;
 
-  e.s = s;
+  e.s = (char *)s;
   e.n = -1;
   r = (struct e *) bsearch (&e, inv_std_dict,
 			    sizeof(inv_std_dict)/sizeof(*inv_std_dict),
@@ -85,7 +85,7 @@ compress (OtpKey key, unsigned wn[])
 }
 
 static int
-get_altword (char *s, void *a)
+get_altword (const char *s, void *a)
 {
   OtpAlgorithm *alg = (OtpAlgorithm *)a;
   int ret;
@@ -102,8 +102,8 @@ get_altword (char *s, void *a)
 
 static int
 parse_words(unsigned wn[],
-	    char *str,
-	    int (*convert)(char *, void *),
+	    const char *str,
+	    int (*convert)(const char *, void *),
 	    void *arg)
 {
   unsigned char *w, *wend, c;
@@ -130,8 +130,9 @@ parse_words(unsigned wn[],
 }
 
 static int
-otp_parse_internal (OtpKey key, char *str, OtpAlgorithm *alg,
-		    int (*convert)(char *, void *))
+otp_parse_internal (OtpKey key, const char *str,
+		    OtpAlgorithm *alg,
+		    int (*convert)(const char *, void *))
 {
   unsigned wn[6];
 
@@ -144,19 +145,19 @@ otp_parse_internal (OtpKey key, char *str, OtpAlgorithm *alg,
 }
 
 int
-otp_parse_stddict (OtpKey key, char *str)
+otp_parse_stddict (OtpKey key, const char *str)
 {
   return otp_parse_internal (key, str, NULL, get_stdword);
 }
 
 int
-otp_parse_altdict (OtpKey key, char *str, OtpAlgorithm *alg)
+otp_parse_altdict (OtpKey key, const char *str, OtpAlgorithm *alg)
 {
   return otp_parse_internal (key, str, alg, get_altword);
 }
 
 int
-otp_parse_hex (OtpKey key, char *s)
+otp_parse_hex (OtpKey key, const char *s)
 {
   char buf[17], *b;
   int is[8];
@@ -183,7 +184,7 @@ otp_parse_hex (OtpKey key, char *s)
 }
 
 int
-otp_parse (OtpKey key, char *s, OtpAlgorithm *alg)
+otp_parse (OtpKey key, const char *s, OtpAlgorithm *alg)
 {
   int ret;
   int dohex = 1;
diff --git a/lib/otp/otp_verify.c b/lib/otp/otp_verify.c
index e70488fa7..26f3c1cac 100644
--- a/lib/otp/otp_verify.c
+++ b/lib/otp/otp_verify.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 1996, 1997 Kungliga Tekniska Högskolan
+ * Copyright (c) 1995 - 2000 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden).
  * All rights reserved.
  * 
@@ -39,7 +39,7 @@ RCSID("$Id$");
 #include "otp_locl.h"
 
 int
-otp_verify_user_1 (OtpContext *ctx, char *passwd)
+otp_verify_user_1 (OtpContext *ctx, const char *passwd)
 {
   OtpKey key1, key2;
 
@@ -58,7 +58,7 @@ otp_verify_user_1 (OtpContext *ctx, char *passwd)
 }
 
 int
-otp_verify_user (OtpContext *ctx, char *passwd)
+otp_verify_user (OtpContext *ctx, const char *passwd)
 {
   void *dbm;
   int ret;