Counting values can be encrypted as a set of counting value cyphertexts according to a hidden vector encryption scheme using sample values of a set of samples, where each of the samples can include multiple sample values. Additionally, tokens can be generated. The tokens can be configured according to the hidden vector encryption scheme, such that each of the tokens can enable decryption of matching cyphertexts. Processing of the counting value cyphertexts and the tokens can be delegated to a map-reduce computer cluster. The cluster can run a map-reduce program to produce and return count representations. Each count representation can represent a count of a set of the counting value cyphertext(s) whose decryption was enabled by one or more of the token(s). For example, the counts may be counts that can be used in constructing a data structure such as a decision tree.