CrypTool-Online

Apps to explore, play around with, and learn about cryptology. For students, teachers, and anyone interested.

Historical encryption 11 apps

Atbash

Simple monoalphabetic substitution cipher originally used on the Hebrew alphabet

Caesar / ROT13

Famous shifting cipher used by Julius Caesar With Python code

Monoalphabetic Substitution

Cipher that replaces letters with letters/characters With Python code

Railfence / Redefence

Transposition cipher that uses a rail fence pattern

Multiplicative

Simple example for affine ciphers

Kamasutra

Involutory substitution cipher described in the Kamasutra (400 BC)

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Modern encryption 4 apps

RSA (explained step by step)

The most widespread asymmetric method for encryption and signing

OpenSSL

Toolkit for general-purpose cryptography with graphical controls in your browser

Private polls (demo)

Conduct a private poll with homomorphic encryption

CryptoBrief

Simple and compact language for cryptographic algorithms

Quantum cryptography 2 apps

Kyber (ML-KEM)

A lattice-based KEM designed to resist cryptanalytic attacks from future powerful quantum computers

BB84 Quantum Key Distribution

Protocol to securely establish a shared key between two parties using quantum mechanics

Cryptanalysis 3 apps

Frequency Analysis

Counts how often text fragments appear in a text

Neural Cipher Identifier

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

Homophonic Substitution Analyzer

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

Codes 3 apps

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

Checks 1 app

Certificate verification

Experiment with certificate validity periods, signature creation and verification dates