Methods and apparatus involve two keys to decode data that are generated during original encoding of the data. The keys are stored on computing devices separate from one another, and the encrypted data, which maintains security until such time as the original data requires decoding. Because the keys can be relatively large, its stored form may have padding bits to align with the file form of the encoded data. Representative keys include a dictionary corresponding to symbols representing the data and a weighted path decoder that correlates the symbols of the dictionary to underlying original bits. A “fast approximation” of compression of current data involves using information obtained from an earlier compression of similar data. Creating the two keys for the original data can also include creating a master key for decoding a plurality of later-encoded files. A second key also works in conjunction with the master key during decoding.