Consider the following attack against one$-$time pad: upon seeing a ciphertextc,

the eavesdropper tries every candidate key k in $\{0,1\}$

$\backslash$lambda until she has found the

one that was used, at which point she outputs the plaintext m$.$ This contradicts

the argument in Section $1\mathrm{.}2$ that the eavesdropper can obtain no information

about m by seeing the ciphertext.