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Determine if key is incorrect with CCCrypt kCCOptionPKCS7Padding-Objective C


Determine if key is incorrect with CCCrypt kCCOptionPKCS7Padding-Objective C

By : user2954910
Date : November 22 2020, 10:33 AM
around this issue kCCDecodeError does not provide information if the correct key is used, just if there are gross errors.
The only way to know if the key is correct is to verify the output. The output can be verified in total or with a hash or other verification such as knowing it should be good output that makes sense in some fashion.
code :


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Obj-C: In CommonCrypto, if the CCCrypt() do not use option kCCOptionPKCS7Padding, the result buffer is empty

Obj-C: In CommonCrypto, if the CCCrypt() do not use option kCCOptionPKCS7Padding, the result buffer is empty


By : Bruce Lilly
Date : March 29 2020, 07:55 AM
wish of those help This is to do with block alignment of input data. If the input data length is not an integer multiple of the encryption block size, then padding will have to be added to finish the final block. There is some discussion of this in the header file for CCCryptorUpdate (CCCrypt is actually CCCryptorCreate, CCCryptorUpdate, CCCryptorFinal and CCCryptorRelease called sequentially):
Issue with Blowfish encryption using kccOptionECBMode and kccOptionPKCS7padding on ios 6

Issue with Blowfish encryption using kccOptionECBMode and kccOptionPKCS7padding on ios 6


By : Wee Han Loh
Date : March 29 2020, 07:55 AM
it helps some times According to the answer i got from the developer forum It is a bug in the older system(i.e. 6.1.) which has been fixed in ios 7 .
So cant help it. One has to write his own algorithm to support ios 6.1.
How can I decrypt a file created in Objective-C using CCCrypt by using openssl?

How can I decrypt a file created in Objective-C using CCCrypt by using openssl?


By : tsmlasvegas
Date : March 29 2020, 07:55 AM
Hope this helps The openssl key and iv as specified with -K and -iv are specified as a hex representation of the binary data.
From the openssl docs:
code :
uint8_t *zeros     = calloc(1, 256);
NSData  *keyData   = [NSData dataWithBytes:zeros length:16];
NSData  *ivData    = [NSData dataWithBytes:zeros length:16];
NSData  *clearData = [@"0123456789abcdef" dataUsingEncoding:NSUTF8StringEncoding];

NSData *encryptedData = [AESTest doCipher:clearData iv:ivData key:keyData context:kCCEncrypt error:&error];
[encryptedData writeToFile:@"/Users/dan/Desktop/encrypted.dat" atomically:YES];
CCCrypt decrypting in AES

CCCrypt decrypting in AES


By : Tim van veenendaal
Date : March 29 2020, 07:55 AM
like below fixes the issue Your use of kCCModeCBC here is incorrect. All CCOption enum values begin with kCCOption. kCCModeCBC is part of the CCMode enum. You can't combine them this way. You're getting away with it because CBC happens to be the default. You should remove | kCCModeCBC. (CCMode is used by a newer interface called CCCryptorCreateWithMode. The interface you're using defaults to CBC and has an option to switch to ECB mode instead.))
To your deeper question, these are bit fields. So "bit zero" (which has a value of 1) is PKCS7 padding. Bit one (which has a value of 2) turns on ECB (not CBC). If you "or" them (which this the same as adding them), you get 3, which means both options. This is an extremely common way to pass boolean data in C, giving each field one bit in a larger integer.
Failed with error 87: The parameter is incorrect. How to determine which parameter is incorrect?

Failed with error 87: The parameter is incorrect. How to determine which parameter is incorrect?


By : user3500750
Date : March 29 2020, 07:55 AM
it should still fix some issue To answer the specific question you asked - the Win32 API does not tell you WHICH parameter is invalid. You have to read the documentation for the function that failed, and then debug your code to compare the values you are actually passing to the function to see how they differ from the acceptable values the function is expecting.
In this particular example, you are passing a NULL pointer to the lpClassName parameter of CreateWindowEx(), which is not allowed. You must specify the name of the window class you want to create.
code :
wstring GetErrorMessage(const wstring &fnName)
{
    DWORD dw = GetLastError();

    wostringstream displayBuffer;
    displayBuffer << fnName << L" failed with error " << dw;

    LPWSTR messageBuffer{};
    if (FormatMessageW(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        0,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPWSTR)&messageBuffer,
        0,
        0))
    {
        displayBuffer << L": " << messageBuffer;
        LocalFree(messageBuffer);
    }

    return displayBuffer.str();
} 
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