Add example how to use tdh2easy

go/tdh2/tdh2easy/easy_test.go

@@ -0,0 +1,80 @@
+/*
+Copy go/tdh2/cmd/demo/main.go from old fork by @WenxingDuan
+https://github.com/WenxingDuan/tdh2/blob/codex/create-demo-for-threshold-encryption-and-decryption/go/tdh2/cmd/demo/main.go
+and convert into a tdh2easy/easy_test.go, similar to tdh2hybridCCP/hybrid_test.go.
+
+TODO: Rekey/"reshare" using Redeal() with the Master Key (ms),
+changed threshold k and/or nodes n if desired, while keeping
+the same shared Public Key that is necessary for randomness verification.
+Then repeat tests with the collective Public Key, as well as
+new n individual Private Key Shares.
+
+Run it together with other `*_test.go` files after change into subdir `tdh2easy`
+of this repo:
+
+~/tdh2/go/tdh2/tdh2easy$ go test
+Original message: hybrid threshold cryptography
+Recovered message: hybrid threshold cryptography
+PASS
+ok      github.com/smartcontractkit/tdh2/go/tdh2/tdh2easy       0.126s
+*/
+package tdh2easy
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+func TestEasy(t *testing.T) {
+	// Optional: Rename this to 'func main() {...}' to convert to
+	// a self-contained Go program. Also replace 't.' by 'log.' and
+	// add prefix 'tdh2easy.' to import functions & objects.
+	// Alternatively, rename it to 'func ExampleEasy()' or similar to test
+	// only for final output, see https://pkg.go.dev/testing#hdr-Examples
+
+	// server generates keys and distributes shares to n nodes with threshold k
+	//k, n := 3, 5
+	k, n := 7, 11
+	//k, n := 99, 120
+	//k, n := 121, 120
+	//ms, pk, shares, err := GenerateKeys(k, n)
+	_, pk, shares, err := GenerateKeys(k, n)
+	if err != nil {
+		t.Fatalf("Failed to generate keys: %v", err)
+	}
+
+	// client encrypts a message using the public key
+	msg := []byte("hybrid threshold cryptography")
+	ctxt, err := Encrypt(pk, msg)
+	if err != nil {
+		t.Fatalf("Encryption failed: %v", err)
+	}
+
+	// min. k of n nodes create decryption shares of the ciphertext
+	decShares := make([]*DecryptionShare, 0, n) // ask all n node to compute
+	//decShares := make([]*DecryptionShare, 0, k) // ask min. threshold k only
+	for i := 0; i < k; i++ { // try any shares between k and n
+		ds, err := Decrypt(ctxt, shares[i])
+		if err != nil {
+			t.Fatalf("Decryption of share %d failed: %v", i, err)
+		}
+		decShares = append(decShares, ds)
+	}
+
+	// server verifies shares and combines them to recover the message
+	for _, s := range decShares {
+		if err := VerifyShare(ctxt, pk, s); err != nil {
+			t.Fatalf("Verify share failed: %v", err)
+		}
+	}
+	recovered, err := Aggregate(ctxt, decShares, n)
+	if err != nil {
+		t.Fatalf("Aggregation of shares failed: %v", err)
+	}
+	if !bytes.Equal(recovered, msg) {
+		t.Fatalf("decrypeted message does not match cleartext\n  got: %#v\n want: %#v", recovered, msg)
+	}
+	fmt.Printf("Original message: %s\n", msg)
+	fmt.Printf("Recovered message: %s\n", recovered)
+}