Converting NSData to SecKeyRef

Question

i have a public key which i gathered from a remote server and i want to perform RSA encryption with that public key. But the problem is i get the public key data as byte arr

Answer 1

Hope It will work....

-(NSData*)convertIOSKeyToASNFormat:(NSData*)iosKey{

    static const unsigned char _encodedRSAEncryptionOID[15] = {
        /* Sequence of length 0xd made up of OID followed by NULL */
        0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
        0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00
    };

    // OK - that gives us the "BITSTRING component of a full DER
    // encoded RSA public key - we now need to build the rest

    unsigned char builder[15];
    NSMutableData * encKey = [[[NSMutableData alloc] init] autorelease];
    int bitstringEncLength;

    // When we get to the bitstring - how will we encode it?
    if  ([iosKey length ] + 1  < 128 )
        bitstringEncLength = 1 ;
    else
        bitstringEncLength = (([iosKey length ] +1 ) / 256 ) + 2 ;

    // Overall we have a sequence of a certain length
    builder[0] = 0x30;    // ASN.1 encoding representing a SEQUENCE

    // Build up overall size made up of -
    size_t i = sizeof(_encodedRSAEncryptionOID) + 2 + bitstringEncLength +
    [iosKey length];

    size_t j = [self encodeLen:&builder[1] length:i];
    [encKey appendBytes:builder length:j +1];

    // First part of the sequence is the OID
    [encKey appendBytes:_encodedRSAEncryptionOID
                 length:sizeof(_encodedRSAEncryptionOID)];

    // Now add the bitstring
    builder[0] = 0x03;
    j = [self encodeLen:&builder[1] length:[iosKey length] + 1];

    builder[j+1] = 0x00;
    [encKey appendBytes:builder length:j + 2];

    // Now the actual key
    [encKey appendData:iosKey];
    return encKey;
}