Re: Obscuring an NSString
Thanks to all who responded. Let me explain my situation a little better. I am storing several string values into an XML file. I want to obscure one of them. When I encrpyt the NSString to an NSdata I can store the data as a string in XML, however when I read the string back in I dont know how to convert it back to NSData to decrypt. Adam On Thu, Dec 2, 2010 at 1:57 PM, Richard Somers rsomers.li...@infowest.com wrote: Try the open source SSCrypto.framework. It is a Cocoa wrapper around OpenSSL encryption and decryption. It works well. http://septicus.com/products/opensource/ --Richard Somers On Dec 2, 2010, at 6:30 AM, Adam Gerson wrote: I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString
On Dec 5, 2010, at 4:31 PM, Adam Gerson wrote: Thanks to all who responded. Let me explain my situation a little better. I am storing several string values into an XML file. I want to obscure one of them. When I encrpyt the NSString to an NSdata I can store the data as a string in XML, however when I read the string back in I dont know how to convert it back to NSData to decrypt. input string (NSString) -- UTF-8 representation (NSData) -- optional encryption such as XOR -- hex string (NSString) this is fully reversible of course. ___ Ricky A. Sharp mailto:rsh...@instantinteractive.com Instant Interactive(tm) http://www.instantinteractive.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString
On Dec 5, 2010, at 2:31 PM, Adam Gerson agers...@gmail.com wrote: Thanks to all who responded. Let me explain my situation a little better. I am storing several string values into an XML file. I want to obscure one of them. When I encrpyt the NSString to an NSdata I can store the data as a string in XML, however when I read the string back in I dont know how to convert it back to NSData to decrypt. You'd better not be treating your XML data as an NSString. ;-) As long as you store your data in a CDATA section, the XML API you're using should give you the ability to get the raw data for a node. Alternatively, one of the convenient properties of Base64 is that it maps your data into a range of printable ASCII characters. So you can treat the Base64 data as ASCII and write it as a string in your XML document (being mindful, of course, of the document's encoding, which is most likely UTF-8 and therefore identical to ASCII for the Base64 output range). Then read it back in as a string, convert it to ASCII, and feed the raw ASCII data into the Base64 decoding algorithm. So to maximize flexibility without involving CDATAs, here's the process I'd use: Saving: Plaintext NSString -- Plaintext NSData (UTF-8; use -dataWithEncoding:) -- Base64 NSData (ASCII) -- Base64 NSString (use +stringWithData:encoding: to create this) -- your XML document Loading: Your XML document -- Base64 NSString (UTF-16) -- Base64 NSData (ASCII characters; use -dataWithEncoding to get this) -- Plaintext NSData (UTF-16) -- NSString (again use +stringWithData:encoding:) HTH, --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Obscuring an NSString
I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. It doesn't have to be major hacker proof, just not understandable by an average person. I need to be able to read the value back in from the file and convert it back to clear text. In php I would just use base64 encode / decode. All the cocoa examples I have found show converting in base64 between nsstring and nsdata. Is there a smiple function I can pass an NSString through to obscure it while keeping it as a string, then reverse it back to clear text in a reliable way? Thanks, Adam ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
RE: Obscuring an NSString (Adam Gerson)
If you convert the NSString into an NSData,(dataUsingEncoding:) and then Base64 encode it into an NSString, doesn't that get you what you want? I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. It doesn't have to be major hacker proof, just not understandable by an average person. I need to be able to read the value back in from the file and convert it back to clear text. In php I would just use base64 encode / decode. All the cocoa examples I have found show converting in base64 between nsstring and nsdata. Is there a smiple function I can pass an NSString through to obscure it while keeping it as a string, then reverse it back to clear text in a reliable way? Thanks, Adam ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString (Adam Gerson)
On 2 Dec 2010, at 17:32, Kirk Kerekes wrote: If you convert the NSString into an NSData,(dataUsingEncoding:) and then Base64 encode it into an NSString, doesn't that get you what you want? Converting the string to an NSData rep and dumping out as a property list will encode the NSData as base-64 + (NSInteger)writePropertyList:(id)plist toStream:(NSOutputStream *)stream format:(NSPropertyListFormat)formatoptions:(NSPropertyListWriteOptions)opt error:(NSError **)error Regards Jonathan Mitchell Developer Mugginsoft LLP http://www.mugginsoft.com___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString
Try the open source SSCrypto.framework. It is a Cocoa wrapper around OpenSSL encryption and decryption. It works well. http://septicus.com/products/opensource/ --Richard Somers On Dec 2, 2010, at 6:30 AM, Adam Gerson wrote: I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString
On Thu, Dec 2, 2010 at 5:30 AM, Adam Gerson agers...@gmail.com wrote: I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. It doesn't have to be major hacker proof, just not understandable by an average person. I need to be able to read the value back in from the file and convert it back to clear text. In php I would just use base64 encode / decode. All the cocoa examples I have found show converting in base64 between nsstring and nsdata. Is there a smiple function I can pass an NSString through to obscure it while keeping it as a string, then reverse it back to clear text in a reliable way? No. You need to go through NSData first. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString (Adam Gerson)
On Thu, Dec 2, 2010 at 9:49 AM, jonat...@mugginsoft.com jonat...@mugginsoft.com wrote: Converting the string to an NSData rep and dumping out as a property list will encode the NSData as base-64 This is an implementation detail. You shouldn't rely on it. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString (Adam Gerson)
On 2 Dec 2010, at 20:37, Kyle Sluder wrote: On Thu, Dec 2, 2010 at 9:49 AM, jonat...@mugginsoft.com jonat...@mugginsoft.com wrote: Converting the string to an NSData rep and dumping out as a property list will encode the NSData as base-64 This is an implementation detail. You shouldn't rely on it. The DTD for plist version 1.0 states: !ELEMENT data (#PCDATA) !-- Contents interpreted as Base-64 encoded -- Therefore I think we can rely on this implementation detail for now. Regards Jonathan Mitchell Developer Mugginsoft LLP http://www.mugginsoft.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Obscuring an NSString
On 03/12/2010, at 12:30 AM, Adam Gerson wrote:
I am writing an NSString to a file and I would like to obscure it in a
two way reversible fashion. It doesn't have to be major hacker proof,
just not understandable by an average person. I need to be able to
read the value back in from the file and convert it back to clear
text. In php I would just use base64 encode / decode. All the cocoa
examples I have found show converting in base64 between nsstring and
nsdata. Is there a smiple function I can pass an NSString through to
obscure it while keeping it as a string, then reverse it back to clear
text in a reliable way?
Lots of ways to do this, but a very simple one is to take advantage of the fact
that A ^ B ^ B = A, in other words, if you XOR something twice you get back the
original.
So convert to bytes [NSString dataUsingEncoding], then XOR each byte with some
constant. Save the data. To recover plain text, XOR with the same constant and
convert back to a string. The constant should not be 0.
Note that this only obfuscates slightly - the text looks pretty scrambled but
is still open to simple techniques such as frequency analysis. If you change
the constant in some predetermined fashion for each byte you can make a much
stronger 'encryption'.
(typed in mail):
- (NSData*) reversiblyObfuscateData:(NSData*) dataIn
{
NSMutableData* dataOut = [NSMutableData data];
NSUInteger n;
char byte;
for( n = 0; n [dataIn length]; ++n )
{
[dataIn getBytes:byte length:1];
byte ^= 0xA5;
[dataOut appendBytes:byte length:1];
}
return dataOut;
}
--Graham___
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Re: Obscuring an NSString
On 2 Dec 2010, at 7:30 AM, Adam Gerson wrote: I am writing an NSString to a file and I would like to obscure it in a two way reversible fashion. It doesn't have to be major hacker proof, just not understandable by an average person. I need to be able to read the value back in from the file and convert it back to clear text. In php I would just use base64 encode / decode. All the cocoa examples I have found show converting in base64 between nsstring and nsdata. Is there a smiple function I can pass an NSString through to obscure it while keeping it as a string, then reverse it back to clear text in a reliable way? Base64 works only bytewise, whereas NSString is notionally UTF-16, so the base64 result really is byte data (representable as NSData), and not a string. If the only purpose of the base64 data is to be the contents of a file, I don't see your objection to its being NSData at the last step before writing and the first step after reading. You already have methods to get an NSString whenever you want it. Why is that not enough? You seem to have a requirement you're not telling us about. — F ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
