New SimpleCrypt page

amanjit

Hi Andre,

Thanks for answering; I wasn't looking for reasonably strong encryption - I just wanted to always get the same encrypted string for the same input (private key+string_to_be_encrypted); its just for private use anyway, and non-critical.

I am using QCryptographicHash for that now, it solves my problem

andre

Eh, no, that class does not solve your problem, if you are indeed looking for encryption rather than hashing. There is a big difference between the two...

amanjit

[quote author="Andre" date="1356878054"]Eh, no, that class does not solve your problem, if you are indeed looking for encryption rather than hashing. There is a big difference between the two... [/quote]

That's a chicken and egg problem: I don't want to elaborate on "my problem" and hence prove that I am fine with hashing because of concerns of privacy. Please understand that and thank you for your help.

topocc

worked in QT 5?

topocc

good thing I changed was this:

@//QString cypherString = QString::fromAscii(cypher.toBase64());
QString cypherString = QString::fromUtf8(cypher.toBase64());

//QString cypherString = QString::fromAscii(cypher.toBase64());
QString cypherString = QString::fromUtf8(cypher.toBase64());

//QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toAscii());
QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toUtf8());

//QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toAscii());
QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toUtf8());@

there will be well done this.

Ian Monroe

I was getting SIGABRT's when attempting to decrypt an empty string with a Qt with debugging enabled. So I've added a little check. Doesn't seem possible to link to wiki history diffs, but you can see it there.

andre

Thanks, good catch.

I assume you're talking about this snippet, right?
@
if( cypher.count() < 3 )
return QByteArray();
@

A small problem is, that no error code is set. I think that needs to be added.

topocc

good, and in QT5 probe, and all good the only thing that was included # include <QDataStream>, and change QString :: fromutf8 () and QString :: toutf8 ().

Clearly only tried with 30 words, and it has worked well.

njeisecke

Hi Andre,

thanks for sharing this very useful code. Works perfectly, did save me quite some time. May I buy you a beer on next DevDays?

Nils

andre

[quote author="njeisecke" date="1362060748"]Hi Andre,

thanks for sharing this very useful code. Works perfectly, did save me quite some time. May I buy you a beer on next DevDays?

Nils[/quote]
Good to hear that. If I'm able to go, you most certainly are welcome to buy me one :-)

pasnox

Hi,

I'm having some troubles using your code.
For the same binary the encryption/decryption of the string using a key works fine.
But if i change the source code and add something like: qWarning() << "what you want";
Then rebuild the app, the password is badly decrypted.

Is this a normal behavior ??

Thanks for your help.

andre

Well, no, of course not. However, your description is so vague that I have no idea what could be wrong.

pasnox

Hi,

Thanks for your answer i found the problem.
I was using a stupid generated test key like: quint64 key( qHash( "the_test_key" ) );
When the binary change, the hash returned by this call was not identical as previously, resulting to badly decrypted content.
Using QString version fixed the problem: quint64 key( qHash( QString( "the_test_key" ) ) );

thanks you!

andre

I don't think qHash is guaranteed to give the same result between runs actually, so it seems unwise to me to use it in this way. Furthermore, it is not very secure. qHash returns a uint, while the key used is a quint64. So, you are only using a 32 bits key instead of a 64 bits one.

pasnox

Right, it's not secure, as i told, it was a test project.
The problem of the qHash over a const char* is that it may be done differently depending the os / compiler.
A qHash around a QString is always giving the same result because it hash the string content - I did not read the code on what it does with const char*.
Anyway, yes using this way is not a good way, but it was a test.
By the way is there some repository to to track the code ? having to copy/paste it from a wiki page is not so natural.

Thanks for your code, and the help.

andre

No the code is not in a repo, but I probably should put it on Gitorious or something like that.

For generating a key out of a string, I think I'd just use QCryptographic hash with MD5 or SHA-1, and create a 64 bit key out of the 16 (MD5) or 20 (SHA-1) bytes these generate. The key you need is 8 bytes, but reducing the 16 or 20 bytes to 8 is just a simple XOR or two away...

butterfingerss

Hey there, I am new to Qt and just came across your work ... great work by the way... could you tell me where your updated work might be? like the latest one?

cuz I seem to have a problem with this one - https://www.gitorious.org/qtdevnet-wiki-mvc/qtdevnet-simplecryptiodevide/source/a170750960820be4230ea1aff85148fc41f0dcf3:

vrushali_deshpande

Hi Andre,

Thanks for the code. It is really useful.

But is there any way to find out whether the file is encrypted or not? I would like to know if the input file is encrypted or not, if yes, then only I will decrypt it.

Thanks in advance,
Vrushali

Kaluss

Hi Andre,
an example how to check it You got directly in the code:

@
if (version !=3) { //we only work with version 3
m_lastError = ErrorUnknownVersion;
qWarning() << "Invalid version or not a cyphertext.";
return QByteArray();
}
@

But is very useful thing that if You send to decryp function non-encypted data it will return the same string.

Kaluss

Hi Andre,
an example how to check it You got directly in the code:

@
if (version !=3) { //we only work with version 3
m_lastError = ErrorUnknownVersion;
qWarning() << "Invalid version or not a cyphertext.";
return QByteArray();
}
@

But is very useful thing that if You send to decryp function non-encypted data it will return the same string.