Vigenere Cipher Examples & Tutorials

Vigenere Cipher Examples

Short examples are the fastest way to see how Vigenere differs from Caesar. The key repeats over the letters, and each plaintext/key pair chooses a different shift.

Example 1: Encrypt HELLO With KEY

Plaintext: H E L L O
Key:       K E Y K E
Shift:     10 4 24 10 4
Cipher:    R I J V S

Result: HELLO encrypted with KEY is RIJVS.

Letter-by-letter:

Plain	Key	Shift	Cipher
H	K	10	R
E	E	4	I
L	Y	24	J
L	K	10	V
O	E	4	S

The two L letters become J and V because they use different key letters.

Example 2: Encrypt ATTACKATDAWN With LEMON

This is the classic classroom example:

Plaintext: A T T A C K A T D A W N
Key:       L E M O N L E M O N L E
Cipher:    L X F O P V E F R N H R

Result: ATTACKATDAWN -> LXFOPVEFRNHR

With spaces preserved for readability:

ATTACK AT DAWN -> LXFOPV EF RNHR

Example 3: Decrypt RIJVS With KEY

Decryption subtracts the same shifts:

Cipher:    R I J V S
Key:       K E Y K E
Shift:     10 4 24 10 4
Plaintext: H E L L O

Result: RIJVS decrypted with KEY is HELLO.

Cipher	Key	Shift	Plain
R	K	10	H
I	E	4	E
J	Y	24	L
V	K	10	L
S	E	4	O

Example 4: A Phrase With Spaces

Most Vigenere tools leave spaces and punctuation in place. The key advances only on letters:

Plaintext: MEET ME
Key:       LEMO NL
Cipher:    XIQH ZP

Result: MEET ME encrypted with LEMON is XIQH ZP.

How to Work Examples by Hand

1. Write the plaintext.
2. Repeat the keyword under the letters.
3. Ignore spaces and punctuation when advancing the key.
4. Add shifts for encryption or subtract shifts for decryption.
5. Check repeated plaintext letters; they should often become different ciphertext letters.

Historical and Classroom Use

Vigenere examples are common in:

• cryptography courses, where they introduce modular arithmetic and polyalphabetic substitution
• CTF challenges, where solvers must identify the cipher and recover the key
• escape-room puzzles, where the keyword can be hidden as a separate clue
• historical cryptography lessons, where students compare Vigenere with Caesar and later machine ciphers

Practice Examples

Try these by hand or in the encoder:

Task	Text	Key	Expected result
Encrypt	CAT	DOG	FON
Encrypt	HELLO	KEY	RIJVS
Decrypt	RIJVS	KEY	HELLO
Encrypt	MEET ME	LEMON	XIQH ZP

Frequently Asked Questions

What is the simplest Vigenere example?

Encrypting HELLO with KEY is a good first example because the key repeats as KEYKE and produces the well-known result RIJVS.

Why do repeated letters encrypt differently?

The key letter changes the shift at each position. A repeated plaintext letter can align with different key letters, so it can produce different ciphertext letters.

Do spaces count when repeating the key?

In most educational implementations, no. Spaces and punctuation are preserved, and the key advances only when a letter is encrypted or decrypted.

What is a good decrypt example?

RIJVS with key KEY decrypts to HELLO. It is short enough to check by hand and shows that decryption subtracts the same shifts used for encryption.

Related Tools

• Encrypt your own text with the Vigenere cipher encoder
• Analyze unknown-key ciphertext with the Vigenere decoder
• Follow row and column lookup on the Vigenere table

Conclusion

Good Vigenere examples make three ideas visible: the repeating key, the per-letter shift, and the way decryption reverses encryption. Once those are clear, longer ciphertext and key-recovery methods are easier to understand.