Added io.Reader/Writers to satisfy io.Copy() interface

Added cmd/main for CLI usage

Signed-off-by: Russ Magee <rmagee@gmail.com>

cmd/main.go

@@ -0,0 +1,33 @@
+// WANDERER - a crypto doodle that appears to give adequate
+// protection to data in a stream cipher context (?)
+//
+// Properties visualized using https://github.com/circulosmeos/circle
+//
+// test command-line 'main' program
+package main
+
+// TODOs:
+// -use a crypto rand (eg mtwist64) instead of go pkg rand?
+// -define s-box rotation/shuffle schema
+// -devise p-box schema
+// ...
+
+import (
+	"flag"
+	"io"
+	"os"
+
+	"blitter.com/go/cryptmt"
+)
+
+var (
+	k string
+)
+
+func main() {
+	flag.StringVar(&k, "k", "WARNING_DEFAULT_KEY", "Key (NOTE insecure specified on command line)")
+	flag.Parse()
+
+	c := cryptmt.New(os.Stdin, os.Stdout, []byte(k))
+	_, _ = io.Copy(c, c)
+}

cryptmt.go

@@ -1,6 +1,6 @@
 // Package CryptMT - implementation of cryptMTv1 stream cipher
-// (but with mtwist64 as base accum) 
-// https://eprint.iacr.org/2005/165.pdf 
+// (but with mtwist64 as base accum)
+// https://eprint.iacr.org/2005/165.pdf
 package cryptmt
 
 // TODO rlm: according to go docs, stream ciphers do not implement the
@@ -11,11 +11,14 @@ package cryptmt
 
 import (
 	"errors"
+	"io"
 
 	mtwist "blitter.com/go/mtwist"
 )
 
 type Cipher struct {
+	r     io.Reader
+	w     io.Writer
 	accum uint64
 	m     *mtwist.MT19937_64
 }
@@ -28,8 +31,8 @@ func (c *Cipher) yield() (r byte) {
 
 // New creates and returns a Cipher. The key argument should be the
 // CryptMT key, 64 bytes.
-func New(key []byte) (c *Cipher) {
-	c = &Cipher{m: mtwist.New()}
+func New(r io.Reader, w io.Writer, key []byte) (c *Cipher) {
+	c = &Cipher{m: mtwist.New(), r: r, w: w}
 	c.m.SeedFullState(key)
 	c.accum = 1
 	// from paper, discard first 64 bytes of output
@@ -39,6 +42,21 @@ func New(key []byte) (c *Cipher) {
 	return c
 }
 
+func (c *Cipher) Read(p []byte) (n int, err error) {
+	n, err = c.r.Read(p)
+	if err == nil {
+		for idx := 0; idx < n; idx++ {
+			p[idx] = p[idx] ^ c.yield()
+		}
+	}
+	return n, err
+}
+
+func (c *Cipher) Write(p []byte) (n int, err error) {
+	n, err = c.w.Write(p)
+	return n, err
+}
+
 // XORKeyStream XORs each byte in the given slice with a byte from the
 // cipher's key stream. Dst and src must overlap entirely or not at all.
 //