Allow shares to be created and combined as bytes rather than strings

sssa.go

@@ -20,6 +20,16 @@ const (
  * share to recreate, of length shares, from the input secret raw as a string
 **/
 func Create(minimum int, shares int, raw string) ([]string, error) {
+	return CreateFromBytes(minimum, shares, []byte(raw))
+}
+
+/**
+ * Returns a new arary of secret shares (encoding x,y pairs as base64 strings)
+ * created by Shamir's Secret Sharing Algorithm requring a minimum number of
+ * share to recreate, of length shares, from the input secret raw as an array
+ * bytes
+**/
+func CreateFromBytes(minimum int, shares int, raw []byte) ([]string, error) {
 	// Verify minimum isn't greater than shares; there is no way to recreate
 	// the original polynomial in our current setup, therefore it doesn't make
 	// sense to generate fewer shares than are needed to reconstruct the secret.
@@ -28,7 +38,7 @@ func Create(minimum int, shares int, raw string) ([]string, error) {
 	}
 
 	// Convert the secret to its respective 256-bit big.Int representation
-	var secret []*big.Int = splitByteToInt([]byte(raw))
+	var secret []*big.Int = splitByteToInt(raw)
 
 	// Set constant prime across the package
 	prime, _ = big.NewInt(0).SetString(DefaultPrimeStr, 10)
@@ -110,7 +120,7 @@ func Create(minimum int, shares int, raw string) ([]string, error) {
  *       or more are passed to this function. Passing thus does not affect it
  *       Passing fewer however, simply means that the returned secret is wrong.
 **/
-func Combine(shares []string) (string, error) {
+func CombineAsBytes(shares []string) ([]byte, error) {
 	// Recreate the original object of x, y points, based upon number of shares
 	// and size of each share (number of parts in the secret).
 	var secrets [][][]*big.Int = make([][][]*big.Int, len(shares))
@@ -122,7 +132,7 @@ func Combine(shares []string) (string, error) {
 	for i := range shares {
 		// ...ensure that it is valid...
 		if IsValidShare(shares[i]) == false {
-			return "", ErrOneOfTheSharesIsInvalid
+			return []byte(""), ErrOneOfTheSharesIsInvalid
 		}
 
 		// ...find the number of parts it represents...
@@ -183,7 +193,21 @@ func Combine(shares []string) (string, error) {
 	}
 
 	// ...and return the result!
-	return string(mergeIntToByte(secret)), nil
+	return mergeIntToByte(secret), nil
+}
+
+/**
+ * Takes a string array of shares encoded in base64 created via Shamir's
+ * Algorithm; each string must be of equal length of a multiple of 88 characters
+ * as a single 88 character share is a pair of 256-bit numbers (x, y).
+ *
+ * Note: the polynomial will converge if the specified minimum number of shares
+ *       or more are passed to this function. Passing thus does not affect it
+ *       Passing fewer however, simply means that the returned secret is wrong.
+**/
+func Combine(shares []string) (string, error) {
+	res, err := CombineAsBytes(shares)
+	return string(res), err
 }
 
 /**

sssa_test.go

@@ -2,6 +2,7 @@ package sssa
 
 import (
 	"testing"
+	"bytes"
 )
 
 func TestCreateCombine(t *testing.T) {
@@ -30,6 +31,32 @@ func TestCreateCombine(t *testing.T) {
 	}
 }
 
+func TestCreateCombineBytes(t *testing.T) {
+	// Short, medium, and long tests
+	testvals := [][]byte{
+		[]byte("N17FigASkL6p1EOgJhRaIquQLGvYV0"),
+		[]byte("0y10VAfmyH7GLQY6QccCSLKJi8iFgpcSBTLyYOGbiYPqOpStAf1OYuzEBzZR"),
+		[]byte("KjRHO1nHmIDidf6fKvsiXWcTqNYo2U9U8juO94EHXVqgearRISTQe0zAjkeUYYBvtcB8VWzZHYm6ktMlhOXXCfRFhbJzBUsXaHb5UDQAvs2GKy6yq0mnp8gCj98ksDlUultqygybYyHvjqR7D7EAWIKPKUVz4of8OzSjZlYg7YtCUMYhwQDryESiYabFID1PKBfKn5WSGgJBIsDw5g2HB2AqC1r3K8GboDN616Swo6qjvSFbseeETCYDB3ikS7uiK67ErIULNqVjf7IKoOaooEhQACmZ5HdWpr34tstg18rO"),
+	}
+
+	minimum := []int{4, 6, 20}
+	shares := []int{5, 100, 100}
+
+	for i := range testvals {
+		created, err := CreateFromBytes(minimum[i], shares[i], testvals[i])
+		if err != nil {
+			t.Fatal("Fatal: creating: ", err)
+		}
+		combined, err := CombineAsBytes(created)
+		if err != nil {
+			t.Fatal("Fatal: combining: ", err)
+		}
+		if !bytes.Equal(combined, testvals[i]) {
+			t.Fatal("Fatal: combining returned invalid data")
+		}
+	}
+}
+
 func TestLibraryCombine(t *testing.T) {
 	shares := []string{
 		"U1k9koNN67-og3ZY3Mmikeyj4gEFwK4HXDSglM8i_xc=yA3eU4_XYcJP0ijD63Tvqu1gklhBV32tu8cHPZXP-bk=",