  We describe the first DNA-based storage architecture that enables random
access to data blocks and rewriting of information stored at arbitrary
locations within the blocks. The newly developed architecture overcomes
drawbacks of existing read-only methods that require decoding the whole file in
order to read one data fragment. Our system is based on new constrained coding
techniques and accompanying DNA editing methods that ensure data reliability,
specificity and sensitivity of access, and at the same time provide
exceptionally high data storage capacity. As a proof of concept, we encoded
parts of the Wikipedia pages of six universities in the USA, and selected and
edited parts of the text written in DNA corresponding to three of these
schools. The results suggest that DNA is a versatile media suitable for both
ultrahigh density archival and rewritable storage applications.
