Private Information Retrieval from Coded Databases with Colluding Servers

We present a general framework for private information retrieval (PIR) from arbitrary coded databases that allows one to adjust the rate of the scheme to the suspected number of colluding servers. If the storage code is a generalized Reed--Solomon code of length $n$ and dimension $k$, we design PIR schemes that achieve a PIR rate of $\frac{n-(k+t-1)}{n}$ while protecting against any $t$ colluding servers, for any $1\leq t\leq n-k$. This interpolates between the previously studied cases of $t=1$ and $k=1$ and achieves PIR capacity in both of these cases asymptotically as the number of files in the database grows.