For the one-time pad system the key must be at least as long as the message.
From the en.wikipedia.org
A scrawled message on a large pad of paper invited solo travelers and singles to make themselves at home in the Living Room and warned children to find another fort.
From the newsday.com
In the corner, a scrawled message on a large pad of paper invited solo travelers and singles to make themselves at home in the Living Room and warned children to find another fort.
From the chron.com
Using a small sketch pad, he wrote out his message in pencil and held it out while he stood across from the picket line.
From the huffingtonpost.com
He listened for three rings but did not leave a message, instead quickly pressing the button in the upper right corner of the pad.
From the denverpost.com
Over at his lonely-bachelor pad, Thomas caught the wink and clicked right back, sending an instant message that led to a real-life date just 48 hours later.
From the sacbee.com
Because these schemes pad the plaintext m with some number of additional bits, the size of the un-padded message M must be somewhat smaller.
From the en.wikipedia.org
If the keyword is as long as the message, chosen random, never becomes known to anyone else, and is never reused, this is the one-time pad cipher, proven unbreakable.