How to get cipheredData from IAGCipheredData object?

Question

How to get cipheredData from IAGCipheredData object?

harishios opened this issue 4 years ago · comments

Hi Team,

Need help here, I need to get the cipheredData and authenticationTagData from the object iagData

IAGCipheredData *iagData = [IAGAesGcm cipheredDataByAuthenticatedEncryptingPlainData:ciphertext
                                                              withAdditionalAuthenticatedData:aad
                                                                      authenticationTagLength:IAGAuthenticationTagLength128
                                                                         initializationVector:iv
                                                                                          key:key
                                                                                        error:nil];

Any help appreciated.

Enrique de la Torre · Answer 1 · Thu Dec 10 2020 06:43:44 GMT+0800 (China Standard Time)

Hi @harishios,

IAGCipheredData is a simple NS class with a few read only properties: https://github.com/indisoluble/AesGcm/blob/master/AesGcm/Classes/IAGCipheredData.h , precisely the values you are looking for.

Hope I could answer your question.

harishios · Answer 2 · Thu Dec 10 2020 06:52:15 GMT+0800 (China Standard Time)

Hi @indisoluble,
Thanks for quick response. I see those are read only properties.

I thought the method cipheredDataByAuthenticatedEncryptingPlainData returns IAGCipheredData in which the prop cipheredData is an encrypted data. Correct me if I'm wrong.

I need an encrypted DATA with AES256 GCM. Could you please help me on that?

Enrique de la Torre · Answer 3 · Thu Dec 10 2020 07:12:49 GMT+0800 (China Standard Time)

There is no cipheredData property in IAGCipheredData, instead you have: cipheredBuffer (which is a pointer to an array of bytes) and cipheredBufferLength (which is the length of the array). You can easily build a NSData instance with those 2 properties.

harishios · Answer 4 · Thu Dec 10 2020 07:49:35 GMT+0800 (China Standard Time)

Thanks @indisoluble: I tried to convert, but no success. Do you have any sample code to convert cipheredBuffer to NSData? Thanks in advance.

Enrique de la Torre · Answer 5 · Thu Dec 10 2020 08:16:55 GMT+0800 (China Standard Time)

Hi again:

Probably, there are some examples in the tests: https://github.com/indisoluble/AesGcm/tree/master/Example/Tests
This explanation here: https://stackoverflow.com/a/41680179 might be useful too
And there are also good examples in the already closed issues: https://github.com/indisoluble/AesGcm/issues?q=is%3Aissue+is%3Aclosed

harishios · Answer 6 · Thu Dec 10 2020 08:17:40 GMT+0800 (China Standard Time)

Thanks @indisoluble, I'm looking into it.