ROT-5 Cipher

ROT5 encryption applies on the digits in a message (ideally made of numbers). It consists in replacing a digit by another by adding 5 (modulo 10).

1234567890
6789012345

Example: 248 is encrypted 793 by ROT-5

For letters, the similar cipher method is ROT13

Decryption of Rot5 is identical to the encryption because Rot5 is reversible.

6789012345
1234567890

Example: 793 re-becomes 248 by ROT-5

ROT-5 converter is used on the digits. Numbers that began with 1 now begin with 6, the 2s become 7s etc. The shifting by 5 continues so on.

According to Benford's law, there should be more 6 than 4 among the first digits of the numbers in the ciphertext.

Rot-5 is already a variant of Rot13, itself a version of Caesar cipher with a shift of 13. Rot-5 is therefore a Caesar cipher with a shift of 5, but applied to an alphabet of digits.

It is common to associate a ROT-13 for coding the letters and ROT-5 for the numbers at the same time.

A shift of 5 allows the code to be reciprocal/reversible/symmetric, this means that 2 consecutive encryptions lead to find the plain number.