  In this note, it is shown that if $f\colon\efq^n\to\efq^n$ is any function
and $\bA=(A_1,..., A_n)$ is uniformly distributed over $\efq^n$, then the
average over $(k_1,...,k_n)\in \efq^n$ of the Renyi (and hence, of the Shannon)
entropy of $f(\bA)+(k_1A_1,...,k_nA_n)$ is at least about $\log_2(q^n)-n$. In
fact, it is shown that the average collision probability of
$f(\bA)+(k_1A_1,...,k_nA_n)$ is at most about $2^n/q^n$.
