add README

README.md

@@ -0,0 +1,55 @@
+# Kotlin OTP
+
+This library provides various [One-Time Password](https://en.wikipedia.org/wiki/One-time_password)
+implementations in Kotlin Multiplatform.
+
+## Features
+
+* [HTOP](https://en.wikipedia.org/wiki/HMAC-based_one-time_password)
+* [TOTP](https://en.wikipedia.org/wiki/Time-based_one-time_password)
+* Multiplatform support
+    * JVM
+    * JavaScript
+    * Native (Linux)
+
+## Installation
+
+Add the following to your `build.gradle.kts`.
+
+```kotlin
+repositories {
+    maven("https://git.infendro.com/api/packages/Infendro/maven")
+}
+
+dependencies {
+    implementation("com.infendro:otp:1.1.1")
+}
+```
+
+## Usage
+
+```kotlin
+import com.infendro.hash.SHA1
+import com.infendro.otp.SecretGenerator
+import com.infendro.otp.TOTP
+import kotlin.time.Clock.System.now
+import kotlin.time.Duration.Companion.seconds
+
+fun main() {
+    // create a TOTP instance using SHA1, a length of 6, and a period of 30 seconds
+    val totp = TOTP(
+        function = SHA1,
+        length = 6,
+        period = 30.seconds,
+    )
+
+    // generate a secret using SHA1
+    val secret = SecretGenerator.generate(SHA1)
+
+    // generate an OTP
+    val otp = totp.generate(secret, now())
+
+    // verify an OTP
+    totp.verify(secret, now(), otp)
+}
+```