Unable to compress large files #2

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1. devthat

   added

   bugSomething isn't workingSomething isn't working

   on Oct 29, 2019
2. devthat commented on Oct 30, 2019

   

   devthat

   on Oct 30, 2019

   Last edited by devthat

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   I tried this out and it eventually works with a 1gb file. The problem however is, that it takes a really long time compared to compressing without a password. I have to investigate this further.
3. devthat

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   enhancementNew feature or requestNew feature or request

   help wantedExtra attention is neededExtra attention is needed

   and removed

   bugSomething isn't workingSomething isn't working

   on Oct 30, 2019
4. auto-Dog commented on Mar 13, 2024

   

   auto-Dog

   on Mar 13, 2024

   Last edited by auto-Dog

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   Seems that compressor and decompressor computes slow if you only use python variable and code to compute. Similar prolem exist in python module ZipFile, where ZipCrypto algorithm are implentment in python.

   https://github.com/devthat/zipencrypt/blob/897f03d05f5b2881e915ed346d0498f58abf3ac8/zipencrypt/zipencrypt3.py#L573C7-L573C20

   I think it might work if cython or C Python API is used to accelerate compute. For example, replace the functions above, using cython. After compile the pyx file, directly use it as a module.

   ** But the speed just doubled with this code, so I also wonder if there's better way to accelerate **

   # in weak_decrypt .pyx
   cdef class weak_decrypt:
       cdef public unsigned long key_0
       cdef public unsigned long key_1
       cdef public unsigned long key_2
   
       def __cinit__(self):
           self.key_0 = 305419896
           self.key_1 = 591751049
           self.key_2 = 878082192
   
       def update_keys(self,int byte):
           crc32 = zlib.crc32
           bytes_c = bytes
           cdef unsigned long factor = 134775813
           self.key_0 = ~crc32(bytes_c((byte,)), ~self.key_0) & 0xFFFFFFFF
           self.key_1 = (self.key_1 + (self.key_0 & 0xFF)) & 0xFFFFFFFF
           self.key_1 = ((self.key_1 * factor) + 1) & 0xFFFFFFFF
           # self.key_1 = ((self.key_1 * 0x8088405) + 1) & 0xFFFFFFFF
           self.key_2 = ~crc32(bytes_c((self.key_1 >> 24,)), ~self.key_2) & 0xFFFFFFFF
       def decrypt(self,chunk):
           chunk = bytearray(chunk)
           cdef int byte
           cdef int i
           cdef int temp
           for i, byte in enumerate(chunk):
               temp = self.key_2 | 2
               byte ^= ((temp * (temp ^ 1)) >> 8) & 0xFF
               self.update_keys(byte)
               chunk[i] = byte
           return bytes(chunk)
   
   # usage in other py file:
   # from weak_decrypt import weak_decrypt
   # dec = weak_decrypt()
   # out = dec.decrypt(input_byte)

   👍React with 👍1Reacted by Jonathan Koch
5. devthat commented on Mar 13, 2024

   

   devthat

   on Mar 13, 2024

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   Nice solution! However, this makes packaging more complicated since you would need to package binaries or do the cython compilation during installation - if that's possible.