diff --git a/lib/des/cbc_cksm.c b/lib/des/cbc_cksm.c
new file mode 100644
index 000000000..d14265330
--- /dev/null
+++ b/lib/des/cbc_cksm.c
@@ -0,0 +1,45 @@
+/* cbc_cksm.c */
+/* Copyright (C) 1993 Eric Young - see README for more details */
+#include "des_locl.h"
+
+u_int32_t des_cbc_cksum(des_cblock (*input), des_cblock (*output), long int length, struct des_ks_struct *schedule, des_cblock (*ivec))
+{
+  register u_int32_t tout0,tout1,tin0,tin1;
+  register long l=length;
+  u_int32_t tin[2],tout[2];
+  unsigned char *in,*out,*iv;
+
+  in=(unsigned char *)input;
+  out=(unsigned char *)output;
+  iv=(unsigned char *)ivec;
+
+  c2l(iv,tout0);
+  c2l(iv,tout1);
+  for (; l>0; l-=8)
+    {
+      if (l >= 8)
+	{
+	  c2l(in,tin0);
+	  c2l(in,tin1);
+	}
+      else
+	c2ln(in,tin0,tin1,l);
+			
+      tin0^=tout0;
+      tin1^=tout1;
+      tin[0]=tin0;
+      tin[1]=tin1;
+      des_encrypt(tin,tout,
+		  schedule,DES_ENCRYPT);
+      /* fix 15/10/91 eay - thanks to keithr@sco.COM */
+      tout0=tout[0];
+      tout1=tout[1];
+    }
+  if (out != NULL)
+    {
+      l2c(tout0,out);
+      l2c(tout1,out);
+    }
+  tout0=tin0=tin1=tin[0]=tin[1]=tout[0]=tout[1]=0;
+  return(tout1);
+}