Index: tests/basic.c
===================================================================
--- tests/basic.c	(revision 1375)
+++ tests/basic.c	(working copy)
@@ -363,6 +363,16 @@
 	  { "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17\xad\x2b\x41\x7b\xe6\x6c\x37\x10",
 	    16,
 	    "\x1e\x03\x1d\xda\x2f\xbe\x03\xd1\x79\x21\x70\xa0\xf3\x00\x9c\xee" },
+	  { "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17\xad\x2b\x41\x7b\xe6\x6c\x37\x10"
+        "\x6c\x37\x10",
+	    19,
+	    "\x46\x92\x63\xbd\xcb\xc5\x0a\x19\x5d\x43\x71\xec\x76\x27\x92\x12"
+        "\x34\xae\x54"},
+	  { "\xf1\x92\x24\x35\xaf\x4f\x9b\x17\xad\x2b\x41\x7b\xe6\x6c\x37\x10"
+        "\x6c\x37\x11",
+	    19,
+	    "\xab\xdf\xc5\x34\x5a\x5c\x51\xc6\x35\x56\xc8\x92\xfd\x57\xee\xbc"
+	    "\x15\x7e\xcf"},
 	}
       },
       {	GCRY_CIPHER_AES192,
Index: cipher/cipher.c
===================================================================
--- cipher/cipher.c	(revision 1375)
+++ cipher/cipher.c	(working copy)
@@ -205,7 +205,19 @@
 
   unsigned char ctr[MAX_BLOCKSIZE];     /* For Counter (CTR) mode. */
 
+  /*This is the context's current position in ctrbuf. Where the number
+    of bytes encrypted are not a multiple of c->cipher_block_size this
+    stores the position of the next byte in the keystream to be xor'd
+    by do_encrypt_ctr. ctr gets incremented every time ctrpos reaches
+    c->cipher_block_size. */
+  unsigned int ctrpos; /* For Counter (CTR) mode. */
 
+  /* This contains the context's current keystream. ctrpos stores the
+     next position to be xor'd in ctrbuf when do_ctr_encrypt is called.
+     The contents of ctr are encrypted every time ctrpos reaches
+     zero in do_ctr_encrypt, and the result is stored in ctrbuf. */
+  byte ctrbuf[MAX_BLOCKSIZE]; /* For Counter (CTR) mode. */
+
   /* What follows are two contexts of the cipher in use.  The first
      one needs to be aligned well enough for the cipher operation
      whereas the second one is a copy created by cipher_setkey and
@@ -921,6 +933,8 @@
   memset (c->u_iv.iv, 0, c->cipher->blocksize);
   memset (c->lastiv, 0, c->cipher->blocksize);
   memset (c->ctr, 0, c->cipher->blocksize);
+  memset (c->ctrbuf, 0, c->cipher->blocksize);
+  c->ctrpos=0;
 }
 
 
@@ -1355,32 +1369,31 @@
     }
 }
 
-
 static void
 do_ctr_encrypt( gcry_cipher_hd_t c, byte *outbuf, const byte *inbuf,
                 unsigned int nbytes )
 {
   unsigned int n;
-  byte tmp[MAX_BLOCKSIZE];
   int i;
+  n = c->ctrpos;
 
-  for(n=0; n < nbytes; n++)
-    {
-      if ((n % c->cipher->blocksize) == 0)
-	{
-	  c->cipher->encrypt (&c->context.c, tmp, c->ctr);
+  while (1) {
+    if (n == 0)
+      c->cipher->encrypt (&c->context.c, c->ctrbuf, c->ctr);
+    do {
+      if (nbytes-- == 0) { c->ctrpos = n; return; }
+      *(outbuf++) = *(inbuf++) ^ c->ctrbuf[n];
+    } while (++n != c->cipher->blocksize);
+    c->ctrpos = n = 0;
+    for (i = c->cipher->blocksize; i > 0; i--)
+      {
+        c->ctr[i-1]++;
+        if (c->ctr[i-1] != 0)
+          break;
+      }
+    if (nbytes == 0) { c->ctrpos = n; return; }
+  }
 
-	  for (i = c->cipher->blocksize; i > 0; i--)
-	    {
-	      c->ctr[i-1]++;
-	      if (c->ctr[i-1] != 0)
-		break;
-	    }
-	}
-
-      /* XOR input with encrypted counter and store in output. */
-      outbuf[n] = inbuf[n] ^ tmp[n % c->cipher->blocksize];
-    }
 }
 
 static void