New SimpleCrypt page
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Aha, got it all sorted out, thanks
I had my suspicions on that, but thought that the "<<" and ">>" operators may use seperate index variables.
Andre: it would be great if you could incorporate in the Example usage code the following so it works out of the box.
@
buffer.open(QIODevice::WriteOnly);
buffer.close();
buffer.open(QIODevice::ReadOnly);
@Because newbies like myself:
- copy + paste + compile
** if it works -> adapt to needs
** if it doesn't -> get lost in the simplest things
Although I must admit that I am learning loads of things through all these problems I get myself into.
Gerolf: Once again thanks for your quick and effective response.
- copy + paste + compile
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paucoma, thank you for your comments and suggestions. I have changed the wiki page accordingly. I am glad you solved the problem, and that it turned out the class itself was not at fault ;-)
I must admit that I wrote the examples directly in the wiki page, and thats when errors like these happen. Sorry about that! I hope the current version is more managable? Note that I was talking about "at the other end", implying that the decryption code was not meant to be used in the same function (and thus, implicitly, with the same buffer).
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Hi Andre,
one suggestion to the wiki page:
In the section SimpleCrypt in use it would be nice to have a list of the encryp/decrypt functions. You state thete are two times 4, but not the names :-)
this means searching inside the code :-)The rest sound really god. Thanks for the article.
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[quote author="Gerolf" date="1300958192"]Hi Andre,
one suggestion to the wiki page:
In the section SimpleCrypt in use it would be nice to have a list of the encryp/decrypt functions. You state thete are two times 4, but not the names :-)
this means searching inside the code :-)The rest sound really god. Thanks for the article.[/quote]
Fair enough, done. :-)
Thanks for the praise.
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Hi Andre,
I'm currently reading your second article, and found the following "here":http://developer.qt.nokia.com/wiki/SimpleCrypt_algorithm_details#00f4e5788aab6d3546bb433842dbbefc :
bq. The payload data block’s contents are encrypted with a four byte (quint64) key.
quint64 is a 64 bit integer, which means 8 byte.
so also in the snipet page, you say:
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SimpleCrypt crypto(Q_UINT64_C(0x7F29B208)); //some random number
@this is just a 32 bit number, not 64 bit.
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void SimpleCrypt::splitKey()
{
m_keyParts.clear();
m_keyParts.resize(4);
for (int i=0;i<4;i++) {
quint64 part = m_key;
for (int j=i; j>0; j--)
part = part >> 8;
part = part & 0xff;
m_keyParts[i] = static_cast<char>(part);
}
}
@this also only uses 4 bytes, not 8.
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some additional topics:
in "Decrypted payload":http://developer.qt.nokia.com/wiki/SimpleCrypt_algorithm_details#2d478ba9ee3cf03e338b506b1a0292dc
SH1 and CRC have the same description:
bq. In case the Protection Checksum flag has been set, the layout of the decrypted payload looks like this:
I think this is just a copy paste error.
As I'm through now, no more things :-)
Very good article, interesting to read. Thanks. -
Hi Andre.
First of all, thanks for sharing your code. :-)I was playing with this algorithm, but I noticed a strange situation: sometimes these work well, sometimes not.
This is the string which I have tested :
10197016915918185882701231384169178913312058269-10750535699546572956586080750006397
The key is: 13775729I tested both with string and binary data (there are several integer values).
So if I encrypt this string, and then decrypt it, sometimes original string is equal with decrypted string, sometimes differ.
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A small test is something like :
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QString cryptSerialNumber;void testCrypt()
{
SimpleCrypt processSimpleCrypt(13775729);
QString uniqueString("10197016915918185882701231384169178913312058269-10750535699546572956586080750006397");
cryptSerialNumber = processSimpleCrypt.encryptToString(uniqueString);
}void testDecrypt()
{
SimpleCrypt processSimpleCrypt(13775729);
QString uniqueString = processSimpleCrypt.decryptToString(cryptSerialNumber);
}
@Sometimes decrypted "uniqueString" is the same as the original, but sometimes is :
1019701691591818588270123138416917891691033658269-10750535699546572956586080750006397, almost the same with original, but not the same :-) -
Well, at least, that narrows down the issue to the decrypting routine... Issue is: there is nothing in there that I can think of might be influenced by something else than the input string itself. I will have to investigate, but I can not do that right now. I'll need a few days before I get around to doing that. Sorry. I would like to encourage you to try to debug it on your own as well. At the very least, insert some debug statements at strategic places in the code to see what goes on.
Hmmmm... now that I think about it: it is actually very strange that your encrypted string stays the same. It should be different each time you do the encryption, even on the same input string. That is because a random byte is inserted at the front of the byte array to encrypt (line 115 and 116 from simplecrypt.cpp).