how to decrypt a large file in java / android -

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main

i looking way encrypt file , decrypt on android device. best solution was: encrypt file openssl decrypt in java using method shown here.

problem: file apparently large (5 mb) , 'out of memory' exception when running on android emulator.

additional

i thankful if add following answer, though if have answer previous section fine:

  1. compression: using zip archive compress encrypted file. has minor effect (20% compression on encrypted file vs 80% on non encrypted version of file). there better way this?
  2. encryption method: able compress file using standard linux commands i.e. openssl aes-256-cbc -a -salt -in password.txt -out password.txt.enc
  3. fast on secure: prefer fast decryption method, on cost of being not secure method.

your main issue you're trying keep in memory (obviously). i'd recommend changes in workflow:

  • get rid of base64-encoding files. there multiple issues that, 1 files larger need be, 1 other need decode encoding (which reduce performance, if tiny bit).
  • do not load data memory (byte arrays). need address issue, that's memory issue comes from. use streams instead of byte array, hold chunks of data in memory.
  • as mentioned in comment, compress before encryption. encrypted data should random numbers, , random numbers can't compressed well. note uncompressing files impacts cpu performance (but goes along faster transmissions)

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