The Wikipedia article "One-time pad ~ Authentication" says :
For example, an attacker who knows that the message contains "meet jane and me tomorrow at three thirty pm" at a particular point can replace that content by any other content of exactly the same length, such as "three thirty meeting is cancelled, stay home", without having access to the one-time pad, a property of all stream ciphers known as malleability.
I don't quite understand how it's possible.
Let's say the string is encrypted using one-pad time. Hacker somehow gets that encrypted text and he knows that the last word contains 6 chars. So, he removes last 6 chars from the ciphertext and he wants to add his own 6 character word. How he can do that?
If he just inserts that word, after the decryption that inserted word becomes most likely just gibberish. Or am I wrong?