Welcome to CrypTool-Online

CrypTool-Online (CTO) is a website to explore, play around with, and learn about ancient and modern cryptography. The aim is to attract students, lecturers, and interested individuals.

Highlights 2

OpenSSL

OpenSSL v3 running locally in your browser

CryptoBrief

Simple and compact language for cryptographic algorithms

Modern encryption 2

RSA (explained step by step)

The most widespread asymmetric method for encryption and signing

Private polls (demo)

Conduct a private poll with homomorphic encryption

Historical encryption 10

Atbash

Simple monoalphabetic substitution cipher originally used on the Hebrew alphabet

Caesar / ROT13

Famous shifting cipher used by Julius Caesar

Monoalphabetic Substitution

Cipher that replaces letters with letters/characters

Railfence / Redefence

Transposition cipher that uses a rail fence pattern

Multiplicative

Simple example for affine ciphers

Kamasutra

Substitution cipher described in the Kamasutra (400 BC)

Enigma

World War 2 rotor encryption machine

Vigenère and variants

First strong polyalphabetic cipher that inspired many other ciphers

XOR

Single bits are XORed (typical component of more complex ciphers)

Bit Shift

Shifts the characters of a text bit by bit

Checksums (hashing) 1

Certificate verification

Experiment with certificate validity periods, signature creation and verification dates. For this example files are already loaded.

Encoding/Decoding 3

ASCII

Letters are replaced by numbers of the ASCII code

Bacon

Coding that hides letters in sentences

Base64

Encodes binary data as a string of 64 distinct printable characters

Cryptanalysis 2

Homophonic Substitution Analyzer

Manual analysis of homophonic substitution ciphers. Among other things for use within the DECRYPT project.

Neural Cipher Identifier

Identifies the cipher type with AI – from just a short given ciphertext