HMAC-SHA1

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Function which returns HMAC-SHA1 encrypted signature composed of public key and secret base string:

QString hmacSha1(QByteArray key, QByteArray baseString)
{
 int blockSize = 64; // HMAC-SHA-1 block size, defined in SHA-1 standard
 if (key.length() > blockSize) { // if key is longer than block size (64), reduce key length with SHA-1 compression
 key = QCryptographicHash::hash(key, QCryptographicHash::Sha1);
 }

QByteArray innerPadding(blockSize, char(0x36)); // initialize inner padding with char "6"
 QByteArray outerPadding(blockSize, char(0x5c)); // initialize outer padding with char "quot;
 // ascii characters 0x36 ("6") and 0x5c ("quot;) are selected because they have large
 // Hamming distance (http://en.wikipedia.org/wiki/Hamming_distance)

for (int i = 0; i < key.length(); i++) {
 innerPadding[i] = innerPadding[i] ^ key.at(i); // XOR operation between every byte in key and innerpadding, of key length
 outerPadding[i] = outerPadding[i] ^ key.at(i); // XOR operation between every byte in key and outerpadding, of key length
 }

// result = hash ( outerPadding CONCAT hash ( innerPadding CONCAT baseString ) ).toBase64
 QByteArray total = outerPadding;
 QByteArray part = innerPadding;
 part.append(baseString);
 total.append(QCryptographicHash::hash(part, QCryptographicHash::Sha1));
 QByteArray hashed = QCryptographicHash::hash(total, QCryptographicHash::Sha1);
 return hashed.toBase64();
}

You may use this code with any license you prefer :)

Note that Qt 5.1 introduces a new class QMessageAuthenticationCode which provides a standard API for HMACs.