add secure methods (#44)

common/src/main/kotlin/ru/touchin/common/byte/ByteUtils.kt

@@ -8,4 +8,12 @@ object ByteUtils {
         }
     }
 
+    fun decodeHex(hex: String): ByteArray {
+        check(hex.length % 2 == 0) { "Must have an even length" }
+
+        return hex.chunked(2)
+            .map { it.toInt(16).toByte() }
+            .toByteArray()
+    }
+
 }

common/src/main/kotlin/ru/touchin/common/random/SecureRandomStringGenerator.kt

@@ -24,4 +24,6 @@ object SecureRandomStringGenerator {
         }
     }
 
+    fun generateRandomBytes(size: Int) = ByteArray(size).also(SecureRandom()::nextBytes)
+
 }