In this paper, we present a privacy preserving encrypted access control scheme to aggregate data for Cloud assisted IoT applications. Our scheme is based on attribute based encryption mechanisms and consists in enciphering a set of data contents, with respect to sub-sets of a general access policy. As such, the gateway is able to decrypt the resulting aggregated data only if it holds the matching certified attributes and it has received a sufficient number of partial ciphertexts. Our construction has several advantages. First, it provides a fine-grained access to aggregated data contents that are enciphered by different multiple encrypting entities. Second, it provides a privacy preserving encryption process, such that a curious gateway can neither identify the enciphering IoT device nor decipher single data chunks. Third, our concrete construction provides low computation and communication costs, adapted to resource-constrained devices, compared to most closely related schemes.