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September 15th, 2013, 03:43 AM  #1 
Newbie Joined: Sep 2013 Posts: 8 Thanks: 0  floating point numbers with modulus(mod)
Hello there, I am working on implementing a search engine algorithm. I have to add noise (which is random float point numbers such as (2.34, 3.12)) on the actual data to be secure. A part of algorithm is dealing with modulus(mod). I can add decimal numbers as a random noise and from that I can retrieve the actual data by using modules(mod). However, when I try to use floatpoint numbers as a noise, I can retrieve the actual data after that!! if I have (A) as actual data. I add noise to this by applying this equation: A' = A+ [Rd] . ra where (A' is the actual data + noise)  [Rd] is the range of the noise such as 20 which is mean the adding noise between 0 to 20  ra is the random noise between 0 to 20. in my case, I can retrieve the actual data by applying this equation: A = A' mod [Rd] However, this is not work with float point numbers!! : ( Is there a way to make this work?! Than you 
September 15th, 2013, 08:29 AM  #2 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: floating point numbers with modulus(mod)
Well, you could floor it after adding the noise. Because I don't understand the purpose of the noise I can't say if this would still do what you want.

September 15th, 2013, 08:35 PM  #3  
Newbie Joined: Sep 2013 Posts: 8 Thanks: 0  Re: floating point numbers with modulus(mod) Quote:
I am try to use Residue number system (RNS) as a search engine. I have to upload small numbers corresponding to text files to Cloud database after converting text files to RNS. The problem is that RNS numbers it is represent actual data which may cause a security problem. So, I have to mask the actual data in cloud to prevent any misuse to retrieve the actual data. However, the mask must not prevent retrieving the actual data that will be used later. Is there any other suggestion to solve this issue? Thank you : )  
September 16th, 2013, 12:53 PM  #4 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: floating point numbers with modulus(mod)
Adding a small amount to a number could completely change the RNS representation of the number. Here's the essential problem. You're telling me that you want to obscure a number so it can't be misused, then use the obscured form of the number. But if you can use the number when obscured, so could the 'bad guys' in the cloud. So it would seem that you need to either add little enough noise that you can work around it with errorcorrecting codes (leaving you with a security vulnerability) or add so much noise that you can't work with the data until it's unobscured. 
September 21st, 2013, 12:22 AM  #5 
Newbie Joined: Sep 2013 Posts: 8 Thanks: 0  Re: floating point numbers with modulus(mod)
Thank you for these comments : )

September 21st, 2013, 02:08 PM  #6 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: floating point numbers with modulus(mod)
I hope it helps!


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