Avoiding encryption of certain blocks in a deduplication vault. In one example embodiment, a method of avoiding encryption of certain blocks during a backup of a source storage into a deduplication vault storage may include analyzing each allocated plain text block stored in a source storage at a point in time to determine if the allocated plain text block is already stored in the deduplication vault storage. If the allocated plain text block is not stored in the deduplication vault storage, the block may be encrypted and the encrypted block may be analyzed to determine if the encrypted block is already stored in the deduplication vault storage. If neither the allocated plain text block nor the encrypted block is already stored in the deduplication vault storage, the encrypted block may be stored in the deduplication vault storage.