Re: How to encrypt string and write to txt

Ok so i got this figured out with this:

stringstream ss;

    for (int i = 0; i < ciphertext.size(); ++i)
    {
        ss << hex << (0xFF & static_cast<byte>(ciphertext[i])) << " ";
    }

    string mystr = ss.str();

    cout << "mystr: " << mystr << endl;


and it works fine, all characters are printed in hex and i can write them 
in a txt file, no problem. BUT when i read them from the txt file, i dont 
know how to convert them back from hex, so i can do the decryption.
On Tuesday, November 29, 2022 at 8:23:19 PM UTC+2 Nikos Karavidas wrote:

> I 've got the following function:
> void encrypt(string ivInString, string keyInString, const string 
> &filename_in, const string &filename_out)
> {
>     SecByteBlock iv(reinterpret_cast<const byte*>(&ivInString[0]), 
> ivInString.size());
>     SecByteBlock key(reinterpret_cast<const byte*>(&keyInString[0]), 
> keyInString.size());
>
>
>     CFB_Mode<AES>::Encryption e;
>     e.SetKeyWithIV(key.data(), key.size(), iv.data());
>
>     ifstream in{ filename_in, ios::binary };
>     ofstream out{ filename_out, ios::binary };
>
>     FileSource f{ in, /*pumpAll=*/true, new StreamTransformationFilter{ e, 
> new FileSink{out} } };
> }
>
> and a similar for decrypting, and they work fine, but this is to encrypt 
> any sort of file, which is my only way of encrypting the txt, but its not 
> what i need. What i need is to encrypt a string. The 1st answer in this 
> link: 
> https://stackoverflow.com/questions/12306956/example-of-aes-using-crypto 
> , prints all the ciphered text in hex in the line that says "cout << "0x" 
> << hex << (0xFF & static_cast<byte>(ciphertext[i])) << " ";". But im not 
> sure how that hex part even works. Do you know how i can write that into a 
> txt file?
>
>
>
> On Tuesday, November 29, 2022 at 7:43:08 PM UTC+2 [email protected] 
> wrote:
>
>> Could you try to write a minimal working example in a separate project 
>> and share the code if you still have any issues? Try to write that 
>> encryption/decryption routines yourself line by line instead of copy&paste 
>> any examples.
>>
>> The idea is simple: you read data source, you put data through the filter 
>> (which does the encryption or decryption) and put the result to the sink. 
>> So you should setup a source: read file in buffer and use StringSource or 
>> VectorSource or use FileSource. Then you should prepare an encryption 
>> filter (StreamTransformationFilter) with appropriate options (you could 
>> learn it from example code). Then you put the data into the Sink.
>> https://www.cryptopp.com/wiki/FileSource
>>
>> Remember to use same key & iv for decryption. Also binary/text mode is 
>> important when reading files. Also remember to use same mode (CBC, ECB, 
>> etc.) for both encryption/decryption algorithm. Use authenticated 
>> encryption to catch message checksum errors.
>>
>> Try to experiment with pipelining, e.g. calculating messag digest and 
>> printing it in hex. When you get the strong feeling what works and what 
>> isn't you could easily use any encryption/decryption algorithm in Cryptopp. 
>> Just take some time to read wiki and experiment with library primitives. 
>> And good luck with that!
>> https://www.cryptopp.com/wiki/Pipelining
>>
>> вторник, 29 ноября 2022 г. в 23:01:33 UTC+7, [email protected]: 
>>
>>> Not sure what you mean by format, i just use something like 
>>> "myFileStream << cipher", and then read it back again. Do you mean that the 
>>> txt file should be utf-8 or something like that? What would be the right 
>>> way to write the ciphered string to the txt file and read it afterwards? 
>>> Thanks a lot for answering btw.
>>>
>>> On Tuesday, November 29, 2022 at 4:15:37 PM UTC+2 [email protected] 
>>> wrote:
>>>
>>>> I think I have an idea of ​​what is happening to you, what happens that 
>>>> you must decrypt in the same format that you encrypted, since that happened 
>>>> to me at some point, you must also see the format in how you return the txt 
>>>> file, or the text of txt if it is the same format that is needed to decrypt 
>>>> it. Greetings.
>>>>
>>>> El lunes, 28 de noviembre de 2022 a las 14:30:04 UTC-5, 
>>>> [email protected] escribió:
>>>>
>>>>> Ok so based on the example from this link   (
>>>>> https://www.cryptopp.com/wiki/Advanced_Encryption_Standard),    i 
>>>>> have tried encrypting a "plain" string into a "cipher" string and writing 
>>>>> that "cipher" string to a .txt file in one program, and in another program 
>>>>> afterwards reading that same .txt file into a string and decrypting it. But 
>>>>> when i cout that "recovered" string, it is just  random characters and not 
>>>>> my original "plain" string. I think the problem starts when i attempt to 
>>>>> get the "cipher" string in the .txt file, but not sure. Any help is greatly 
>>>>> appreciated. Thanks in advance.
>>>>
>>>>

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