Initial data commit

Task/Elliptic-Curve-Digital-Signature-Algorithm/Go/elliptic-curve-digital-signature-algorithm.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+    "crypto/ecdsa"
+    "crypto/elliptic"
+    "crypto/rand"
+    "crypto/sha256"
+    "encoding/binary"
+    "fmt"
+    "log"
+)
+
+func check(err error) {
+    if err != nil {
+        log.Fatal(err)
+    }
+}
+
+func main() {
+    priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+    check(err)
+    fmt.Println("Private key:\nD:", priv.D)
+    pub := priv.Public().(*ecdsa.PublicKey)
+    fmt.Println("\nPublic key:")
+    fmt.Println("X:", pub.X)
+    fmt.Println("Y:", pub.Y)
+
+    msg := "Rosetta Code"
+    fmt.Println("\nMessage:", msg)
+    hash := sha256.Sum256([]byte(msg)) // as [32]byte
+    hexHash := fmt.Sprintf("0x%x", binary.BigEndian.Uint32(hash[:]))
+    fmt.Println("Hash   :", hexHash)
+
+    r, s, err := ecdsa.Sign(rand.Reader, priv, hash[:])
+    check(err)
+    fmt.Println("\nSignature:")
+    fmt.Println("R:", r)
+    fmt.Println("S:", s)
+
+    valid := ecdsa.Verify(&priv.PublicKey, hash[:], r, s)
+    fmt.Println("\nSignature verified:", valid)
+}