import base64
import hashlib
import hmac
import struct
import time
def generate_totp(secret_base32: str, timestamp: int = None, step: int = 30, digits: int = 6) -> str:
"""
Generiert ein RFC 6238-konformes TOTP-Token.
:param secret_base32: Geteilter Geheimschlüssel im Base32-Format (z. B. ‘JBSWY3DPEHPK3PXP’)
:param timestamp: Unix-Epochenzeitstempel in Sekunden. Standardmäßig aktuelle Zeit
:param step: Zeitintervallfenster in Sekunden (Standard: 30)
:param digits: Anzahl der Ausgabeziffern (Standard: 6)
:return: Mit Nullen links aufgefüllter OTP-String (z. B. ‘045812’)
"""
if timestamp is None:
timestamp = int(time.time())
1. Base32-String normalisieren und mit ’=’ auf Vielfaches von 8 auffüllen
normalized_secret = secret_base32.replace(” ”, "").upper()
padding_needed = (8 - len(normalized_secret) % 8) % 8
normalized_secret += ”=” * padding_needed
key_bytes = base64.b32decode(normalized_secret)
2. 64-Bit Big-Endian Zeitschritt-Zähler T berechnen
time_counter = timestamp // step
time_bytes = struct.pack(“>Q”, time_counter)  # 8 Bytes Big-Endian unsigned long long
3. HMAC-SHA1-Digest berechnen (20 Bytes)
hmac_digest = hmac.new(key_bytes, time_bytes, hashlib.sha1).digest()
4. Dynamisches Abschneiden (Dynamic Truncation)
offset = hmac_digest[-1] & 0x0F  # Untere 4 Bits des 20. Bytes
4 Bytes ab Offset entpacken und MSB-Vorzeichenbit löschen
binary_code = struct.unpack(“>I”, hmac_digest[offset : offset + 4])[0] & 0x7FFFFFFF
5. Modulo-Arithmetik und Formatierung mit führenden Nullen
otp_code = binary_code % (10 ** digits)
return str(otp_code).zfill(digits)
if name == “main”:
test_secret = “JBSWY3DPEHPK3PXP”
print(f”Berechneter TOTP-Code: {generate_totp(test_secret)}”)

const crypto = require('crypto');
// RFC 4648 Base32-Decoder in nativem JavaScript
function base32Decode(base32Str) {
const alphabet = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ234567’;
const cleaned = base32Str.replace(/=+$/, ”).toUpperCase().replace(/\s+/g, ”);
let bits = 0, value = 0, index = 0;
const output = new Uint8Array(Math.floor((cleaned.length * 5) / 8));
for (let i = 0; i < cleaned.length; i++) {
const val = alphabet.indexOf(cleaned[i]);
if (val === -1) continue;
value = (value << 5) | val;
bits += 5;
if (bits >= 8) {
output[index++] = (value >>> (bits - 8)) & 255;
bits -= 8;
}
}
return Buffer.from(output.buffer, 0, index);
}
function generateTOTP(secretBase32, timestamp = Math.floor(Date.now() / 1000), step = 30, digits = 6) {
const key = base32Decode(secretBase32);
const counter = Math.floor(timestamp / step);
// 8-Byte Puffer im Big-Endian-Format allozieren
const buffer = Buffer.alloc(8);
buffer.writeBigUInt64BE(BigInt(counter), 0);
// HMAC-SHA1 berechnen
const hmac = crypto.createHmac(‘sha1’, key).update(buffer).digest();
// Dynamisches Abschneiden (Dynamic Truncation)
const offset = hmac[hmac.length - 1] & 0x0f;
const binary = ((hmac[offset] & 0x7f) << 24) |
((hmac[offset + 1] & 0xff) << 16) |
((hmac[offset + 2] & 0xff) << 8) |
(hmac[offset + 3] & 0xff);
const otp = binary % (10 ** digits);
return otp.toString().padStart(digits, ‘0’);
}
console.log(“Berechneter TOTP:”, generateTOTP(“JBSWY3DPEHPK3PXP”));

async function generateBrowserTOTP(secretBase32, timestamp = Math.floor(Date.now() / 1000)) {
const keyBytes = base32Decode(secretBase32);
const counter = Math.floor(timestamp / 30);
// 1. Rohe Schlüssel-Bytes in SubtleCrypto importieren
const cryptoKey = await window.crypto.subtle.importKey(
“raw”,
keyBytes,
{ name: “HMAC”, hash: { name: “SHA-1” } },
false,
[“sign”]
);
// 2. 8-Byte Big-Endian Zählerpuffer erzeugen
const buffer = new ArrayBuffer(8);
const view = new DataView(buffer);
view.setBigUint64(0, BigInt(counter), false); // false = Big-Endian
// 3. Kryptografische HMAC-Signatur berechnen
const signature = await window.crypto.subtle.sign(“HMAC”, cryptoKey, buffer);
const hmacResult = new Uint8Array(signature);
// 4. Dynamisches Abschneiden
const offset = hmacResult[hmacResult.length - 1] & 0x0f;
const binary = ((hmacResult[offset] & 0x7f) << 24) |
((hmacResult[offset + 1] & 0xff) << 16) |
((hmacResult[offset + 2] & 0xff) << 8) |
(hmacResult[offset + 3] & 0xff);
const otp = binary % 1000000;
return otp.toString().padStart(6, ‘0’);
}

package main
import (
“crypto/hmac”
“crypto/sha1”
“encoding/base32”
“encoding/binary”
“fmt”
“math”
“strings”
“time”
)
// GenerateTOTP berechnet standardkonforme RFC 6238 zeitbasierte Einmalkennwörter
func GenerateTOTP(secretBase32 string, timestamp int64, step int64, digits int) (string, error) {
// 1. Base32-Seed bereinigen und dekodieren
cleaned := strings.ToUpper(strings.ReplaceAll(secretBase32, ” ”, ""))
key, err := base32.StdEncoding.WithPadding(base32.NoPadding).DecodeString(cleaned)
if err != nil {
key, err = base32.StdEncoding.DecodeString(cleaned)
if err != nil {
return "", err
}
}
// 2. 64-Bit Big-Endian Zeitschritt-Zähler kodieren
counter := uint64(timestamp / step)
buf := make([]byte, 8)
binary.BigEndian.PutUint64(buf, counter)
// 3. HMAC-SHA1 berechnen
mac := hmac.New(sha1.New, key)
mac.Write(buf)
hash := mac.Sum(nil)
// 4. Dynamisches Abschneiden
offset := hash[len(hash)-1] & 0x0f
binaryCode := binary.BigEndian.Uint32(hash[offset:offset+4]) & 0x7fffffff
// 5. Modulo-Arithmetik
mod := uint32(math.Pow10(digits))
otp := binaryCode % mod
format := fmt.Sprintf(“%%0%dd”, digits)
return fmt.Sprintf(format, otp), nil
}
func main() {
code, err := GenerateTOTP(“JBSWY3DPEHPK3PXP”, time.Now().Unix(), 30, 6)
if err != nil {
panic(err)
}
fmt.Printf(“Golang berechneter TOTP: %s\n”, code)
}