starting WASM wrapper

README.md

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+# Shamir Secret Sharing [![Go Report Card](https://goreportcard.com/badge/github.com/arnaucube/shamirsecretsharing)](https://goreportcard.com/report/github.com/arnaucube/shamirsecretsharing) [![GoDoc](https://godoc.org/github.com/arnaucube/shamirsecretsharing?status.svg)](https://godoc.org/github.com/arnaucube/shamirsecretsharing)
+This repo contains a Go lang implementation of Shamir Secret Sharing, and a compiled Web Assembly version from the Go code to be used from the browser.
+
+- https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing
+
+## Wasm usage
+Compile to wasm, inside the `wasm` directory, execute:
+```
+GOARCH=wasm GOOS=js go build -o shamirsecretsharing.wasm shamirsecretsharing-wasm-wrapper.go
+```
+
+Add the file `wasm_exec.js` in the directory:
+```
+cp "$(go env GOROOT)/misc/wasm/wasm_exec.js" .
+```
+
+Call the library from javascript:
+```js
+// Create shares from a secret
+// nNeededShares: number of secrets needed
+// nShares: number of shares
+// p: random point
+// k: secret to share
+createShares(nNeededShares, nShares, p, k);
+```
+
+## Usage from Go
+```go
+// define secret to share
+k, ok := new(big.Int).SetString("123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890", 10)
+assert.True(t, ok)
+
+// define random prime
+p, err := rand.Prime(rand.Reader, bits/2)
+assert.Nil(t, err)
+
+// define how many shares want to generate
+nShares := big.NewInt(int64(6))
+
+// define how many shares are needed to recover the secret
+nNeededShares := big.NewInt(int64(3))
+
+// create the shares
+shares, err := Create(
+	nNeededShares,
+	nShares,
+	p,
+	big.NewInt(int64(k)))
+assert.Nil(t, err)
+
+// select shares to use
+var sharesToUse [][]*big.Int
+sharesToUse = append(sharesToUse, shares[2])
+sharesToUse = append(sharesToUse, shares[1])
+sharesToUse = append(sharesToUse, shares[0])
+
+// recover the secret using Lagrange Interpolation
+secr := LagrangeInterpolation(sharesToUse, p)
+
+// check that the restored secret matches the original secret
+if !bytes.Equal(k.Bytes(), secr.Bytes()) {
+	fmt.Println("reconstructed secret not correspond to original secret")
+}
+```

go.mod

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+module github.com/arnaucube/shamirsecretsharing
+
+go 1.12
+
+require github.com/stretchr/testify v1.3.0

go.sum

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+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=

wasm/shamirsecretsharing-wasm-wrapper.go

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+package main
+
+import (
+	"math/big"
+	"syscall/js"
+
+	"github.com/arnaucube/shamirsecretsharing"
+)
+
+func main() {
+	c := make(chan struct{}, 0)
+
+	println("WASM Go Initialized")
+	// register functions
+	registerCallbacks()
+	<-c
+}
+
+func registerCallbacks() {
+	js.Global().Set("createShares", js.ValueOf(createShares))
+	js.Global().Set("lagrangeInterpolation", js.ValueOf(lagrangeInterpolation))
+}
+
+func createShares(i []js.Value) {
+	nNeededShares, ok := new(big.Int).SetString(i[0].String(), 10)
+	if !ok {
+		println("error parsing parameter in position 0")
+	}
+	nShares, ok := new(big.Int).SetString(i[1].String(), 10)
+	if !ok {
+		println("error parsing parameter in position 1")
+	}
+	p, ok := new(big.Int).SetString(i[2].String(), 10)
+	if !ok {
+		println("error parsing parameter in position 2")
+	}
+	k, ok := new(big.Int).SetString(i[3].String(), 10)
+	if !ok {
+		println("error parsing parameter in position 3")
+	}
+	shares, err := shamirsecretsharing.Create(nNeededShares, nShares, p, k)
+	if err != nil {
+		println("error generating the shares")
+	}
+	println(shares)
+}
+
+func lagrangeInterpolation(i []js.Value) {
+}