Vigenere encryption

src/main/kotlin/Encryption/VigenereEncryption.kt

@@ -0,0 +1,24 @@
+fun vigenere(text: String, key: String, encrypt: Boolean = true): String {
+    val t = if (encrypt) text.toUpperCase() else text
+    val sb = StringBuilder()
+    var ki = 0
+    for (c in t) {
+        if (c !in 'A'..'Z') continue
+        val ci = if (encrypt)
+            (c.toInt() + key[ki].toInt() - 130) % 26
+        else
+            (c.toInt() - key[ki].toInt() +  26) % 26
+        sb.append((ci + 65).toChar())
+        ki = (ki + 1) % key.length
+    }
+    return sb.toString()
+}
+
+fun main(args: Array<String>) {
+    val key = "LEMON"
+    val text = "ATTACKATDAWN"
+    val encoded = vigenere(text, key)
+    println(encoded)
+    val decoded = vigenere(encoded, key, false)
+    println(decoded)
+}

src/test/kotlin/Encryption/VigEncTest.kt

@@ -0,0 +1,29 @@
+import org.junit.Test
+import java.util.*
+
+class VigEncTest {
+    @Test
+    fun testWithAttackAtDawnString() {
+        val secretText = "ATTACKATDAWN"
+        val key = "LEMON"
+        val encoded = vigenere(secretText, key)
+        assert(vigenere(encoded, key, false)==secretText)
+
+    }
+    @Test
+    fun testWithIntellIjString() {
+        val secretText = "INTELLIJJIDEA"
+        val key = "CIPHER"
+        val encoded = vigenere(secretText, key)
+        assert(vigenere(encoded, key, false)==secretText)
+
+    }
+    @Test
+    fun testWithAlgorithmjString() {
+        val secretText = "ALGORITHMREPO"
+        val key = "LEMON"
+        val encoded = vigenere(secretText, key)
+        assert(vigenere(encoded, key, false)==secretText)
+
+    }
+}