Vigenère Calculator

[Back] This page defines a Vigenère Calculator. One of the most wide used examples is to take attackatdawn with a code word of lemon Here, and it should give lxfopvefrnhr [Vigenere (reverse)][Vigenere crack].

Enter Sentence:
Enter Key:

Code:

Decode (just to check):

How Vigenère works?

For example, if we use a key of KING:

Plain a b c d e f g h i j k l m n o p q r s t u v w x y z 
 6    g h i j k l m n o p q r s t u v w x y z a b c d e f
 8    i j k l m n o p q r s t u v w x y z a b c d e f g h
10    k l m n o p q r s t u v w x y z a b c d e f g h i j
13    n o p q r s t u v w x y z a b c d e f g h i j k l m

For example phase becomes zpnyo, as p (read row 10 for K) gives Z, h (read row 8 for I) gives P, a (read row 13 for N) gives n), and so on.

The great advantage of this type of code is that the same plaintext character will be encrypted with different values, depending on the position of the keyword. For example, if the keyword is GREEN, ‘e’ can be encrypted as ‘K’ (for G), ‘V’ (for R), ‘I’ (for E) and ‘R’ (for N). To improve the security, the greater the size of the code word, the more the rows that can be included in the encryption process. Also, it is not possible to decipher the code by a frequency analysis, as letters will change their coding depending on the current position of the keyword. It is also safe from analysis of common two- and three-letter occurrences, if the keysize is relatively long. For example ‘ee’ could be encrypted with ‘KV’ (for GR), ‘VI’ (for RE), ‘II’ (for EE), ‘IR’ (for EN) and ‘RK’ (for NG) [Example].

Plain a b c d e f g h i j k l m n o p q r s t u v w x y z 
1     b c d e f g h i j k l m n o p q r s t u v w x y z a
2     c d e f g h i j k l m n o p q r s t u v w x y z a b
3     d e f g h i j k l m n o p q r s t u v w x y z a b c
4     e f g h i j k l m n o p q r s t u v w x y z a b c d 
5     f g h i j k l m n o p q r s t u v w x y z a b c d e
6     g h i j k l m n o p q r s t u v w x y z a b c d e f
7     h i j k l m n o p q r s t u v w x y z a b c d e f g
8     i j k l m n o p q r s t u v w x y z a b c d e f g h
9     j k l m n o p q r s t u v w x y z a b c d e f g h i
10    k l m n o p q r s t u v w x y z a b c d e f g h i j
11    l m n o p q r s t u v w x y z a b c d e f g h i j k
12    m n o p q r s t u v w x y z a b c d e f g h i j k l
13    n o p q r s t u v w x y z a b c d e f g h i j k l m
14    o p q r s t u v w x y z a b c d e f g h i j k l m n
15    p q r s t u v w x y z a b c d e f g h i j k l m n o
16    q r s t u v w x y z a b c d e f g h i j k l m n o p
17    r s t u v w x y z a b c d e f g h i j k l m n o p q
18    s t u v w x y z a b c d e f g h i j k l m n o p q r
19    t u v w x y z a b c d e f g h i j k l m n o p q r s
20    u v w x y z a b c d e f g h i j k l m n o p q r s t
21    v w x y z a b c d e f g h i j k l m n o p q r s t u
22    w x y z a b c d e f g h i j k l m n o p q r s t u v
23    x y z a b c d e f g h i j k l m n o p q r s t u v w
24    y z a b c d e f g h i j k l m n o p q r s t u v w x
25    z a b c d e f g h i j k l m n o p q r s t u v w x y

Frequency Analysis of Text

This table shows the occurances of the letters in the text (ignoring the case of the letters):

Mapping to normal

This table shows how the text matches a normal probability to text (where 'E' has the highest level of occurance and 'Z' has the least). The grey rows show what would be expected for the order, and the red one shows what your text gives for the order:

Frequency Analysis

Examples

Try "help" with a key of "green". Try!, which should give: nvpt
Try "john" with a key of "ink". Try!, which should give: rbrv
Try "attackatdawn" with a key of "lemon". Try!, which should give: LXFOPVEFRNHR Check
Try "aged twenty six.." with a key of "encrypt". Try! Check