SimplePrivacy 4+

SimplePrivacy uses a very simple to understand and at the same time effective one-time pad encryption technique - you could do this with pencil and paper, but SimplePrivacy will make it much easier for you.
Every character of your text will be encrypted or decrypted with one character of your key by just adding them together:

Plaintext: HELLO
Key: ABCDE
Encrypted Text: HFNOS

Encryption:
H + A = H
E + B = F
L + C = N
L + D = O
O + E = S

Decryption:
H - A = H
F - B = E
N - C = L
O - D = L
S - E = O

If the key contains real random characters and is only used once for the encryption/decryption of a text this is a very safe encryption technique. But be careful: if you use the same key twice, your secret key can be easily discovered with the help of crypto-analysis.

You can group the characters of the encrypted/decrypted texts to different word lengths and you can share your texts with other applications. SimplePrivacy also provides a consolidated view where you can directly see how the encryption works, by putting plaintext (blue), key (red) and encrypted text (green) below each other.