Instead of transferring a large original file, such as a virtual-machine image file, from a source system to a target system, the original file is encoded to define a recipe file that is transferred. The recipe is then decoded to yield a duplicate of the original file on the target system. Encoding involves identifying standard blocks in the original file and including standard-block identifiers for the standard blocks in the recipe in lieu of the original blocks. Decoding involves an exchange with a standard-block identifier server system, which provides standard blocks in response to received standard-block identifiers.