Some time ago i’ve asked in this forum how i could encrypt a large file on an iphone without loading them entirely into memory. Didn’t get an answer though. I didn’t want to load megabytes of data to ram only to encrypt them again … in ram. iDevices have very limited ram so i wanted the encryption engine to encrypt files instead of in-memory data, not loading the entire file to memory. I am not an expert in objective-c so i did not find a way to do this usin Security.framework. Instead, i wrote a class that reads a source file in specified size chunks, encrypts them and writes to a destination file. This way i’m not reading an entire file into memory so that solves my problem. However … does that raise another completely different problem? Does the encryption suffer if i split the file in N parts, encrypt those parts separately and then join the result into an encrypted file? I have virtually no knowledge in cryptography so i want to make sure if my approach does not compromise the cryptography algorithm (i’m using AES 128bit).
Thanks for sharing your thoughts
The encryption of a file does not suffer from being done in chunks because the encryption is ALWAYS done in small chunks. AES (what you seemed to be using in your prior question) has a chunk size of 128 bits.