Importance

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Abstract

Described are methods and systems for encrypting and decrypting configuration data for programmable logic devices. An encrypted bitstream of configuration data includes two or more portions, each of which may be encrypted using a different key. Prior to loading, the author of each portion calculates the byte count for his or her portion and loads the required decryption key and byte count into a key and count memory. The designs are then loaded together as a single bitstream. The PLD decrypts the first portions using the first password. At the start of the partial bitstream, configuration logic loads the count associated with the decryption key for the first portions into a decrementing counter. The counter then decrements for each byte decrypted, reaching a count of zero when the first portion is fully decrypted. The configuration logic then selects the subsequent decryption key and associated count for the next portion of the bitstream.

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First Claim