Data commit

Task/RSA-code/Go/rsa-code.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+    "fmt"
+    "math/big"
+)
+
+func main() {
+    var n, e, d, bb, ptn, etn, dtn big.Int
+    pt := "Rosetta Code"
+    fmt.Println("Plain text:            ", pt)
+
+    // a key set big enough to hold 16 bytes of plain text in
+    // a single block (to simplify the example) and also big enough
+    // to demonstrate efficiency of modular exponentiation.
+    n.SetString("9516311845790656153499716760847001433441357", 10)
+    e.SetString("65537", 10)
+    d.SetString("5617843187844953170308463622230283376298685", 10)
+
+    // convert plain text to a number
+    for _, b := range []byte(pt) {
+        ptn.Or(ptn.Lsh(&ptn, 8), bb.SetInt64(int64(b)))
+    }
+    if ptn.Cmp(&n) >= 0 {
+        fmt.Println("Plain text message too long")
+        return
+    }
+    fmt.Println("Plain text as a number:", &ptn)
+
+    // encode a single number
+    etn.Exp(&ptn, &e, &n)
+    fmt.Println("Encoded:               ", &etn)
+
+    // decode a single number
+    dtn.Exp(&etn, &d, &n)
+    fmt.Println("Decoded:               ", &dtn)
+
+    // convert number to text
+    var db [16]byte
+    dx := 16
+    bff := big.NewInt(0xff)
+    for dtn.BitLen() > 0 {
+        dx--
+        db[dx] = byte(bb.And(&dtn, bff).Int64())
+        dtn.Rsh(&dtn, 8)
+    }
+    fmt.Println("Decoded number as text:", string(db[dx:]))
+}