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javasecurityperformancedigital-signaturejca

Check the signature on large data sets efficiently using JCA

I have to verify the signature on a file that may be as large as 2Gb, and I want to do so in a way that is as memory-efficient as possible. For various reasons, the file will already be loaded completely into memory, and is accessed using an InputStream by the application. I would like to verify the signature using the stream interface, but the JCA Signature class' update method only accepts byte[] and related classes.

How can I do this efficiently? I don't want to load the beast into a second byte array, otherwise we'll be seeing some seriously high memory use, but the interface doesn't seem to support it otherwise.

Update

If it matters, the signing algorithm is SHA-1

Solution

  • Why not just read the input stream a block (4096bytes or whatever convenient size) at a time, call update() for each block.