https://bugzilla.novell.com/show_bug.cgi?id=760434
https://bugzilla.novell.com/show_bug.cgi?id=760434#c0 Summary: BigInteger.Parse("1").ModInverse incorrectly throws ArithmeticException if modulus >0xFFFFFFFF Classification: Mono Product: Mono: Class Libraries Version: 2.8.x Platform: 32bit OS/Version: Windows 7 Status: NEW Severity: Major Priority: P5 - None Component: Mono.Security AssignedTo: fr...@suse.com ReportedBy: andyr...@digitalforces.com QAContact: mono-bugs@lists.ximian.com Found By: --- Blocker: --- User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.168 Safari/535.19 i=ModInverse(x,p) is supposed to return i such that i*x (modulus p) is 1. For i to exist, x and p have to be co-prime. Ie: gcd(x,p)=1. In particular, ModInverse(1,p)=1 for all values of p>1. In mono, the function BigInteger.ModInverse works for x=1 as long as p<=0xFFFFFFFF. For larger p's, it incorrectly throws ArithmeticException ("No inverse!") Reproducible: Always Steps to Reproduce: Open MonoDevelop on Windows 7/32, add a reference to Mono.Security. Paste and run this code: using System; using Mono.Math;//needs Mono.Security reference namespace ModInverse { class MainClass { public static void Main (string[] args) { Console.WriteLine (BigInteger.Parse("1").ModInverse(BigInteger.Parse("4294967296"))); } } } Actual Results: Unhandled Exception: System.ArithmeticException: No inverse! at Mono.Math.BigInteger+Kernel.modInverse (Mono.Math.BigInteger bi, Mono.Math. BigInteger modulus) [0x00106] in C:\cygwin\tmp\monobuild\build\BUILD\mono-2.10.8 \mcs\class\Mono.Security\Mono.Math\BigInteger.cs:2364 at Mono.Math.BigInteger.ModInverse (Mono.Math.BigInteger modulus) [0x00000] in C:\cygwin\tmp\monobuild\build\BUILD\mono-2.10.8\mcs\class\Mono.Security\Mono.Ma th\BigInteger.cs:888 Expected Results: 1 The error does not ocurr for p between 0 and 2^32-1. The error does not seem to ocurr for x!=1. Here is a little more info on modInverse: http://docs.oracle.com/javase/1.4.2/docs/api/java/math/BigInteger.html#modInverse(java.math.BigInteger) -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the QA contact for the bug. _______________________________________________ mono-bugs maillist - mono-bugs@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-bugs
