Vigenere encryption online
Simply explained and directly applied!
By Brandon T. Fields(cdated) – This W3C-unspecified vector graphic was created with Inkscape., Public domain, Link
Discover the world of encryption!
The Vigenère cipher is a polyalphabetic cipher that was developed to improve the Caesar cipher was developed. The plaintext is encrypted using a keyword, which means that the shift can change for each letter.
Wie funktioniert die Vigenère Verschlüsselung?
Vigenère encryption method
- Select keyword:
- Example: Keyword = “LEMON”
- This word is repeated until it reaches the length of the plain text.
- Set up plain text:
- Example: Plain text = “HELLO WORLD”
- Encrypt each letter with the keyword:
- Each letter of the plain text is shifted additively with the corresponding letter from the keyword.
- The Vigenère table (an extended Caesar encryption) is used for this purpose.
Result: The encrypted text is “SIXZB HSDZQ”.
The Vigenère encryption online
With the small app you can try out Vigenere encryption for yourself.
And this is how Vigenere encryption works online with a keyword:
- Enter the plain text to be encrypted.
- Then enter the keyword.
- Click on the “Verschlüssele” button to encode the message with the Vignere cipher.
- In the table you will then see the plain text, the repeating key, the shift per letter and the “encrypted text”.
Try it out straight away! You should have tested our Caesar disk and Caesar encryption beforehand so that you can see the difference.
Vigenère encryption online
Result
Security of Vigenère encryption
Advantages of Vigenère encryption
✅ Safer than Caesar
No simple frequency analysis possible.
✅ Easy to implement
No complex math required.
✅ Flexible due to keyword
Can generate very different texts depending on the key.
Disadvantages of Vigenère encryption
❌ Periodicity of the key
If the keyword is short, it is often repeated and can be decoded by Kasiski testing.
❌ Not absolutely safe
Cryptanalysis using statistical methods can reconstruct the key when long texts are analyzed.
Comparison with Caesar encryption
| Feature | Caesar encryption | Vigenère encryption |
|---|---|---|
| Displacement | Fixed shift | Varies by keyword |
| key | Number (e.g. +3) | Word (e.g. “LEMON”) |
| security | Easy to crack (brute force with 26 possibilities) | Significantly more secure, as several shifts |
| Analysis by frequencies | Simple (e.g. “E” occurs frequently) | Much more difficult, as there is no fixed pattern |
Vigenere Verschlüsselung als Python – Code
Would you like to write your own program in Python to perform a Vigenere cipher? Here we have created a small Python program for you.
def vigenere_encrypt(klartext, schluessel):
klartext = klartext.upper().replace(” “, “”) # Entferne Leerzeichen und setze Großbuchstaben
schluessel = schluessel.upper()
verschluesselter_text = “”
schluessel_wiederholt = “”
shifts = []
for i in range(len(klartext)):
key_char = key[i % len(schluessel)]
shift = ord(key_char) – ord(‘A’)
shifts.append(shift)
enc_char = chr(((ord(plain_text[i]) – ord(‘A’) + shift) % 26) + ord(‘A’))
encrypted_text += enc_char
key_repeated += key_char
return encrypted_text, key_repeated, shifts
# Example:
plaintext = “HELLO WORLD”
key = “LEMON”
cipher, key_repeated, shifts = vigenere_encrypt(plaintext, key)
print(“Plain text: “, klartext)
print(“Key: “, schluessel_wiederholt)
print(“Shifts: “, shifts)
print(“Ciphertext: “, chiffre)
Explanation of the Python program for Vigenere encryption:
ATTENTION: the copyable text is not formatted correctly and does not contain the correct spaces as inserts and the quotation marks may be incorrect when copied into your system. Therefore the correctly formatted code is shown in an image! You can simply download the Python code for Vigenère encryption as a *.txt file.
The Python program for the Vigenère cipherthat generates the plain text in the variable klartext and the key in schluessel is stored.
The program removes spaces, encrypts the text and outputsthe encrypted text, the repeated key characters and the shifts.gt ensures that the shift remains in the 26-letter alphabet.
FAQ – Vigenère encryption explained simply
1 What is Vigenère encryption?
Vigenère encryption is a polyalphabetic encryption method that uses a repeated key text for encryption. Each letter of the plaintext is linked to a letter of the key, resulting in different shifts.
2 How does Vigenère encryption work?
The method is based on Caesar encryption, whereby the shift per character is determined by the respective letter of the keyword. The formula is This is the ciphered letter, the plain text letter and the key letter.
3. what are the advantages of Vigenère encryption?
-
Stronger than simple Caesar encryption
-
Complicates the frequency analysis
-
Relatively easy to implement and understand
4 What are the weaknesses of Vigenère encryption?
-
If the keyword is too short, it is repeated and makes the encryption vulnerable.
-
The method can be broken down by the Kasiski test and the Friedman analysis.
5. how can the Vigenère encryption be cracked?
-
Kasiski testFinds repeated strings to determine the length of the key.
-
Friedman testStatistical method for determining the key length.
-
Brute force attackPossible if the keyword is short.
How does Vigenère cipher differ from the Caesar cipher?
Caesar encryption uses a fixed shift for all letters, while Vigenère encryption uses a varying key text that changes the shift for each letter. This makes it much more secure than simple Caesar encryption.
7 Where is Vigenère encryption still used today?
Today, the Vigenère cipher is mostly used for educational purposes in cryptography. It served as the basis for more modern encryption methods and helps to understand basic concepts of encryption.
Practice encrypting Caesar texts
Continue playing and practicing Caesar encryption online with our online program!
