[Qt-interest] QCA big string encryption
Nicholas Shatokhin
n.shatokhin at gmail.com
Sun Apr 24 23:25:24 CEST 2011
What is the shared-secret cypher?
Mon, 25 Apr 2011 00:23:40 +0300 було написано Jason H <scorp1us at yahoo.com>:
> Ah, good observation.
>
> It should be know that SSL only uses asymmetric encryption for key and
> cypher
> exchange. The stream itself uses a shared-secret cypher.
>
>
>
>
> ----- Original Message ----
> From: Jeroen De Wachter <jeroen.dewachter at elis.ugent.be>
> To: Nicholas Shatokhin <n.shatokhin at gmail.com>
> Cc: qt-interest at qt.nokia.com
> Sent: Sun, April 24, 2011 5:14:20 PM
> Subject: Re: [Qt-interest] QCA big string encryption
>
> Hey Nicholas,
>
> Have you seen the maximumEncryptSize function in PublicKey?
> Your string might simply be too big...
>
> http://delta.affinix.com/docs/qca/classQCA_1_1PublicKey.html#175b61ba787f95146b5971295120f8b8
>
>
> Also, AFAIK asymmetric encryption algorithms are usually used on small
> amounts of data because of their intense CPU load. IIRC, they are
> typically used to encrypt the key of a symmetric encryption algorithm,
> which is usually easier on the CPU (and thus faster for processing
> copious amounts of data). Can you tell us why you would need to process
> such a large string?
>
> Kind regards,
>
> Jeroen
>
> On Sun, 2011-04-24 at 22:15 +0300, Nicholas Shatokhin wrote:
>> I'm sorry, but I must finish it in few hours and I don't know how.
>>
>> Sun, 24 Apr 2011 22:06:22 +0300 було написано Jason H
>> <scorp1us at yahoo.com>:
>>
>> > Generally you need an IV (Initialization vector) this then is fed to
>> the
>> > routines with the keys. The IV is an important random number so that
>> if
>> > you can
>> > encrypt the same message with the same keys multiple times and not get
>> > the same
>> > encrypted message (thus ruling out a dictionary attack)
>> >
>> > Anyway, there are two types of cyphers, block and stream. With block
>> > cyphers,
>> > you work a block at a time. The last block will usually be incomplete,
>> > and there
>> > is some final[ize[() method for handling this special block. Normally,
>> > the
>> > enc/decrypt functions in QCA will give you all complete blocks,
>> leaving
>> > you to
>> > call finalize().
>> >
>> > QCA does have convince functions that will do it all without you
>> having
>> > to call
>> > finalize(), HOWEVER this should only be used for messages of known,
>> short
>> > lengths. The non-convenience functions are designed to be used in a
>> > streaming
>> > manner, which is better for memory and scalability.
>> >
>> >
>> >
>> > HTH, but AFAIAC, this is a QCA question, not a Qt question.
>> >
>> >
>> >
>> >
>> > ----- Original Message ----
>> > From: Nicholas Shatokhin <n.shatokhin at gmail.com>
>> > To: qt-interest at qt.nokia.com; Jason H <scorp1us at yahoo.com>
>> > Sent: Sun, April 24, 2011 2:52:53 PM
>> > Subject: Re: [Qt-interest] QCA big string encryption
>> >
>> > What do you mean?
>> >
>> > There is my code below. What must I add? (I use 1024bit rsa key and
>> > message
>> > truncate to 1024bit)
>> >
>> >
>> > bool CCryptor::generateKeys(int size)
>> > {
>> > if(init())
>> > {
>> > QCA::PrivateKey seckey = QCA::KeyGenerator().createRSA(size);
>> >
>> > if(seckey.isNull())
>> > {
>> > std::cout << "Failed to make private RSA key" <<
>> std::endl;
>> > return false;
>> > }
>> >
>> > QCA::PublicKey pubkey = seckey.toPublicKey();
>> >
>> > privateKey = seckey;
>> > publicKey = pubkey;
>> >
>> > return true;
>> > }
>> > else
>> > return false;
>> > }
>> >
>> > QByteArray CCryptor::dataEnrypt(QByteArray data)
>> > {
>> > // check if the key can encrypt
>> > if(!publicKey.canEncrypt())
>> > {
>> > std::cout << "Error: this kind of key cannot encrypt" <<
>> > std::endl;
>> > return QByteArray();
>> > }
>> >
>> > QCA::SecureArray arg = data;
>> >
>> > // encrypt some data - note that only the public key is required
>> > // you must also choose the algorithm to be used
>> > QCA::SecureArray result = publicKey.encrypt(arg,
>> > QCA::EME_PKCS1_OAEP);
>> >
>> > if(result.isEmpty()) {
>> > std::cout << "Error encrypting" << std::endl;
>> > return QByteArray();
>> > }
>> >
>> > return result.toByteArray();
>> > }
>> >
>> > QByteArray CCryptor::dataDecrypt(QByteArray data)
>> > {
>> > QCA::SecureArray encrypt = data;
>> > QCA::SecureArray decrypt;
>> > if(0 == privateKey.decrypt(encrypt, &decrypt,
>> QCA::EME_PKCS1_OAEP))
>> > {
>> > std::cout << "Error decrypting.\n";
>> > return QByteArray();
>> > }
>> >
>> > return decrypt.data();
>> > }
>> >
>> >
>> >
>> > Sun, 24 Apr 2011 21:31:38 +0300 було написано Jason H
>> > <scorp1us at yahoo.com>:
>> >
>> >> It's beena while since I used QCA, but do you need to finalize() it
>> >> for the
>> >> last block?
>> >>
>> >>
>> >>
>> >>
>> >> ----- Original Message ----
>> >> From: Nicholas Shatokhin <n.shatokhin at gmail.com>
>> >> To: qt-interest at qt.nokia.com
>> >> Sent: Sun, April 24, 2011 1:12:41 PM
>> >> Subject: [Qt-interest] QCA big string encryption
>> >>
>> >> Hello.
>> >>
>> >> I'm trying to encrypt end decrypt long string. But after decryption,
>> I
>> >> get
>> >> only part of string. What's wrong?
>> >>
>> >> Code:
>> >>
>> >> QCA::SecureArray arg = data;
>> >> qDebug() << arg.toByteArray();
>> >> QCA::SecureArray result = publicKey.encrypt(arg,
>> >> QCA::EME_PKCS1_OAEP);
>> >> privateKey.decrypt(result, &arg, QCA::EME_PKCS1_OAEP);
>> >> qDebug() << arg.toByteArray();
>> >>
>> >> Output:
>> >>
>> >> "{"method": 1, "data": {"email": "dfgh", "usePassword": "false",
>> >> "password": "", "useFingerprint": false, "fingerprint": "",
>> "publicKey":
>> >>
>> "LS0tLS1CRUdJTiBQVUJMSUMgS0VZLS0tLS0KTUlHZk1BMEdDU3FHU0liM0RRRUJBUVVBQTRHTkFEQ0JpUUtCZ1FDN05UNjd6R1pHajZpbDc5K3ErOWo5K2s5cApnVHJJOGxRVlFoQkxuVWxBNFArS01selBEOU9aOEk0UXRWNEdjT0ZOYWFyTjByZFlacllKaVF2VjBUQkdSSnRWCnNEOTVsZzNPMHFzVHBuSVdrYW5rUTVFUmdiTDlqQ0grb0taNFBrUEd0OW9MVjhCOGphNjFRazdhLytBVUZ1UUQKeDBMUGZvUyt5VkVoYXNjM0x3SURBUUFCCi0tLS0tRU5EIFBVQkxJQyBLRVktLS0tLQo="}
>>
>> >> }
>> >> }"
>> >>
>> >> "{"method": 1, "data": {"email": "dfgh", "usePassword": "false",
>> >> "password": "", "useFi"
>> >>
>> >>
>> >> Best regards,
>> >> Nick.
>> >>
>> >
>> >
>> > --За використання революційного клієнта електронної пошти Opera:
>> > http://www.opera.com/mail/
>> >
>>
>>
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