sending encrypted data via mail using smtp

[vermarajeev]

The order while sending should be:
1. encrypt file
2. encode it with base64
3. divide it into blocks 64 (or 80 or whatever) bytes each
4. concatenate blocks using newlines (\r\n)
5. pass the result into the mail stream adding a base64 header

when receiving a mail:
1. parse headers
2. concatenate lines
3. base64 decode into QByteArray
4. decrypt
5. pass the result into the stream

Did you mean this below code

while sending

int MAX_BLK_SIZE = 64;
      string sSrcBlk = dat;
      int hManyBlks =  sSrcBlk.length()/MAX_BLK_SIZE;
      char** pSrcBlk = new char*[hManyBlks + 1];
 
    for( int i=0; i < hManyBlks; ++i )
     {
          pSrcBlk[i] = new char[MAX_BLK_SIZE + 1];
          memcpy(pSrcBlk[i], sSrcBlk.data(), MAX_BLK_SIZE);
     }
 
      //append the block 
      for( int i=0; i < hManyBlks; ++i )
	QString blks = QString( pSrcBlk[i] ) + QString("\r\n");
 
	//send blks through mail stream adding base64 header

int MAX_BLK_SIZE = 64;
      string sSrcBlk = dat;
      int hManyBlks =  sSrcBlk.length()/MAX_BLK_SIZE;
      char** pSrcBlk = new char*[hManyBlks + 1];

    for( int i=0; i < hManyBlks; ++i )
     {
          pSrcBlk[i] = new char[MAX_BLK_SIZE + 1];
          memcpy(pSrcBlk[i], sSrcBlk.data(), MAX_BLK_SIZE);
     }

      //append the block 
      for( int i=0; i < hManyBlks; ++i )
	QString blks = QString( pSrcBlk[i] ) + QString("\r\n");

	//send blks through mail stream adding base64 header

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while receiving

1) parse -- How to do this ?
2) contcatenate lines -- How to do this ?
3) base64 decode into ByteArray -- I can do it
4) decrypt ---- I can do it
5) pass the result into the stream -- I can do it

1) parse -- How to do this ?
2) contcatenate lines -- How to do this ?
3) base64 decode into ByteArray -- I can do it
4) decrypt ---- I can do it
5) pass the result into the stream -- I can do it

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[wysota]

I'm unable to understand these points
3. divide it into blocks 64 (or 80 or whatever) bytes each ---- need some more explanation
4. concatenate blocks using newlines (\r\n) ----- ---- need some more explanation
5. pass the result into the mail stream adding a base64 header --------- ---- need some more explanations
If possible please correct me with my code above and tell me how can I achieve the above three points

Ad 3. and 4. base64 encoded data is a string of characters. The usual thing to do is to divide the long line into shorter lines.
Ad 5. Make the result part of your outgoing mail embedding it into proper attachment headers.

Something like:

QString base64encoded; // your encoded data here
QStringList slist;
while(base64encoded.length()>64){
  slist << base64encoded.left(64);
  base64encoded.remove(0, 64);
}
slist << base64encoded; // remainder
 
QString result = slist.join("\x0a\x0C"); // \r\n

QString base64encoded; // your encoded data here
QStringList slist;
while(base64encoded.length()>64){
  slist << base64encoded.left(64);
  base64encoded.remove(0, 64);
}
slist << base64encoded; // remainder

QString result = slist.join("\x0a\x0C"); // \r\n

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while receiving

1) parse -- How to do this ?
2) contcatenate lines -- How to do this ?
3) base64 decode into ByteArray -- I can do it
4) decrypt ---- I can do it
5) pass the result into the stream -- I can do it

1) parse -- How to do this ?
2) contcatenate lines -- How to do this ?
3) base64 decode into ByteArray -- I can do it
4) decrypt ---- I can do it
5) pass the result into the stream -- I can do it

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Oh come on... I'm not going to write a mail client for you Use your head - think.

[vermarajeev]

Thank you wysota,
It is a long time that I have send the post and till then I have been trying to solve the problem. And the good thing is I'm just near to solution. I'm able to send the encrypted data, and also able to decode it but only partial i.e only half. I think there is a problem using std::string with binary data.

I'm just trying to figure out and let you know if I get.
I'm really sorry to ask for solution without myself going in depth.

Thanks

[wysota]

Why do you use std::string for binary data? It should be safe anyway (contrary to using QString)... You should simply use QByteArray and its data() method if you need to operate on the raw data directly.