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  • Security review of an authenticated Diffie Hellman variant

    - by mtraut
    EDIT I'm still hoping for some advice on this, i tried to clarify my intentions... When i came upon device pairing in my mobile communication framework i studied a lot of papers on this topic and and also got some input from previous questions here. But, i didn't find a ready to implement protocol solution - so i invented a derivate and as i'm no crypto geek i'm not sure about the security caveats of the final solution: The main questions are Is SHA256 sufficient as a commit function? Is the addition of the shared secret as an authentication info in the commit string safe? What is the overall security of the 1024 bit group DH I assume at most 2^-24 bit probability of succesful MITM attack (because of 24 bit challenge). Is this plausible? What may be the most promising attack (besides ripping the device out off my numb, cold hands) This is the algorithm sketch For first time pairing, a solution proposed in "Key agreement in peer-to-peer wireless networks" (DH-SC) is implemented. I based it on a commitment derived from: A fix "UUID" for the communicating entity/role (128 bit, sent at protocol start, before commitment) The public DH key (192 bit private key, based on the 1024 bit Oakley group) A 24 bit random challenge Commit is computed using SHA256 c = sha256( UUID || DH pub || Chall) Both parties exchange this commitment, open and transfer the plain content of the above values. The 24 bit random is displayed to the user for manual authentication DH session key (128 bytes, see above) is computed When the user opts for persistent pairing, the session key is stored with the remote UUID as a shared secret Next time devices connect, commit is computed by additionally hashing the previous DH session key before the random challenge. For sure it is not transfered when opening. c = sha256( UUID || DH pub || DH sess || Chall) Now the user is not bothered authenticating when the local party can derive the same commitment using his own, stored previous DH session key. After succesful connection the new DH session key becomes the new shared secret. As this does not exactly fit the protocols i found so far (and as such their security proofs), i'd be very interested to get an opinion from some more crypto enabled guys here. BTW. i did read about the "EKE" protocol, but i'm not sure what the extra security level is.

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  • Another Nim's Game Variant

    - by Terry Smith
    Given N binary sequence Example : given one sequence 101001 means player 0 can only choose a position with 0 element and cut the sequence from that position {1,101,1010} player 1 can only choose a position with 1 element ans cut the sequence from that position {null,10,101000} now player 0 and player 1 take turn cutting the sequence, on each turn they can cut any one non-null sequence, if a player k can't make a move because there's no more k element on any sequence, he lose. Assume both player play optimally, who will win ? I tried to solve this problem with grundy but i'm unable to reduce the sequence to a grundy number because it both player don't have the same option to move. Can anyone give me a hint to solve this problem ?

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  • Ubuntu Variant / Linux Distros which uses least system resources (RAM, CPU)?

    - by elegantonyx
    I have a netbook (an older Asus EEEPC 1005HA) which I want to get rid of Windoze on (I like Windows, but I don't think it works well in a netbook environment). Basically, my question is which Ubuntu variant will use the least RAM and CPU running idle, and/or the same question except when running Firefox and Libreoffice Writer, say. I am also open to suggestions of non-Ubuntu Linux distros, but since this is AskUbuntu I thought the first question would be more appropriate. I have a disk drive which I can attach to the netbook, so it doesn't have to be a Ubuntu Variant / Linux Distro which solely boots from a USB drive. I have at my disposal: DVDs, DVD writer/ disk drive, 4gb flash drive, 8 gb flash drive I was thinking either Lubuntu or Archbang / Crunchbang but I would like some help from more knowledgable people Specs: Can't boot into it right now, but I think I have either Intel Atom N270 @1.60ghz OR Intel Atom N280 @1.66ghz (single core, I think) 2gb RAM 160 GB hard drive

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  • Calling Matlab's MLApp.MLAppClass.FEval from F#

    - by Matthew
    Matlab provides a COM interface that supports remote execution of arbitrary functions (and code snippets). In particular, it has an Feval method that calls a given Matlab function. The third parameter to this method, pvarArgOut, has COM type VARIANT*, and appears in the Visual Studio F# editor as an argument of type: pvarArgOut: byref<obj> The following code calls interp1, which in Matlab returns a matrix (i.e. 2D double array) result, as is normal for most Matlab functions. let matlab = new MLApp.MLAppClass() let vector_to_array2d (v : vector) = Array2D.init v.Length 1 (fun i j -> v.[i]) let interp1 (xs : vector) (ys : vector) (xi : vector) = let yi : obj = new obj() matlab.Feval("interp1", 1, ref yi, vector_to_array2d xs, vector_to_array2d ys, vector_to_array2d xi) yi :?> float[,] This code compiles fine, but when calling interp1, I get a COM exception: A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll Additional information: Invalid callee. (Exception from HRESULT: 0x80020010 (DISP_E_BADCALLEE)) I get the same error whether initialize yi with a new obj, a new Array2D, or null. How does F# translate VARIANT output arguments?

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  • What's the recommended implemenation for hashing OLE Variants?

    - by Barry Kelly
    OLE Variants, as used by older versions of Visual Basic and pervasively in COM Automation, can store lots of different types: basic types like integers and floats, more complicated types like strings and arrays, and all the way up to IDispatch implementations and pointers in the form of ByRef variants. Variants are also weakly typed: they convert the value to another type without warning depending on which operator you apply and what the current types are of the values passed to the operator. For example, comparing two variants, one containing the integer 1 and another containing the string "1", for equality will return True. So assuming that I'm working with variants at the underlying data level (e.g. VARIANT in C++ or TVarData in Delphi - i.e. the big union of different possible values), how should I hash variants consistently so that they obey the right rules? Rules: Variants that hash unequally should compare as unequal, both in sorting and direct equality Variants that compare as equal for both sorting and direct equality should hash as equal It's OK if I have to use different sorting and direct comparison rules in order to make the hashing fit. The way I'm currently working is I'm normalizing the variants to strings (if they fit), and treating them as strings, otherwise I'm working with the variant data as if it was an opaque blob, and hashing and comparing its raw bytes. That has some limitations, of course: numbers 1..10 sort as [1, 10, 2, ... 9] etc. This is mildly annoying, but it is consistent and it is very little work. However, I do wonder if there is an accepted practice for this problem.

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  • What's the recommended implementation for hashing OLE Variants?

    - by Barry Kelly
    OLE Variants, as used by older versions of Visual Basic and pervasively in COM Automation, can store lots of different types: basic types like integers and floats, more complicated types like strings and arrays, and all the way up to IDispatch implementations and pointers in the form of ByRef variants. Variants are also weakly typed: they convert the value to another type without warning depending on which operator you apply and what the current types are of the values passed to the operator. For example, comparing two variants, one containing the integer 1 and another containing the string "1", for equality will return True. So assuming that I'm working with variants at the underlying data level (e.g. VARIANT in C++ or TVarData in Delphi - i.e. the big union of different possible values), how should I hash variants consistently so that they obey the right rules? Rules: Variants that hash unequally should compare as unequal, both in sorting and direct equality Variants that compare as equal for both sorting and direct equality should hash as equal It's OK if I have to use different sorting and direct comparison rules in order to make the hashing fit. The way I'm currently working is I'm normalizing the variants to strings (if they fit), and treating them as strings, otherwise I'm working with the variant data as if it was an opaque blob, and hashing and comparing its raw bytes. That has some limitations, of course: numbers 1..10 sort as [1, 10, 2, ... 9] etc. This is mildly annoying, but it is consistent and it is very little work. However, I do wonder if there is an accepted practice for this problem.

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  • Better variant of getting the output dinamically-allocated array from the function?

    - by Raigomaru
    Here is to variants. First: int n = 42; int* some_function(int* input) { int* result = new int[n]; // some code return result; } void main() { int* input = new int[n]; int* output = some_function(input); delete[] input; delete[] output; } Here the function returns the memory, allocated inside the function. Second variant: int n = 42; void some_function(int* input, int* output) { // some code } void main() { int* input = new int[n]; int* output = new int[n]; some_function(input, output); delete[] input; delete[] output; } Here the memory is allocated outside the function. Now I use the first variant. But I now that many built-in c++ functions use the second variant. The first variant is more comfortable (in my opinion). But the second one also has some advantages (you allocate and delete memory in the same block). Maybe it's a silly question but what variant is better and why?

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  • boost::spirit::karma using the alternatives operator (|) with conditions

    - by Ingemar
    I'm trying to generate a string from my own class called Value using boost::spirit::karma, but i got stuck with this. I've tried to extract my problem into a simple example. I want to generate a String with karma from instances of the following class: class Value { public: enum ValueType { BoolType, NumericType }; Value(bool b) : type_(BoolType), value_(b) {} Value(const double d) : type_(NumericType), value_(d) {}; ValueType type() { return type_; } operator bool() { return boost::get<bool>(value_); } operator double() { return boost::get<double>(value_); } private: ValueType type_; boost::variant<bool, double> value_; }; Here you can see what I'm tying to do: int main() { using karma::bool_; using karma::double_; using karma::rule; using karma::eps; std::string generated; std::back_insert_iterator<std::string> sink(generated); rule<std::back_insert_iterator<std::string>, Value()> value_rule = bool_ | double_; Value bool_value = Value(true); Value double_value = Value(5.0); karma::generate(sink, value_rule, bool_value); std::cout << generated << "\n"; generated.clear(); karma::generate(sink, value_rule, double_value); std::cout << generated << "\n"; return 0; } The first call to karma::generate() works fine because the value is a bool and the first generator in my rule also "consumes" a bool. But the second karma::generate() fails with boost::bad_get because karma tries to eat a bool and calls therefore Value::operator bool(). My next thought was to modify my generator rule and use the eps() generator together with a condition but here i got stuck: value_rule = (eps( ... ) << bool_) | (eps( ... ) << double_); I'm unable to fill the brackets of the eps generator with sth. like this (of course not working): eps(value.type() == BoolType) I've tried to get into boost::phoenix, but my brain seems not to be ready for things like this. Please help me! here is my full example (compiling but not working): main.cpp

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  • SCons: How to use the same builders for multiple variants (release/debug) of a program

    - by OK
    The SCons User Guide tells about the usage of Multiple Construction Environments to build build multiple versions of a single program and gives the following example: opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') o = opt.Object('foo-opt', 'foo.c') opt.Program(o) d = dbg.Object('foo-dbg', 'foo.c') dbg.Program(d) Instead of manually assigning different names to the objects compiled with different environments, VariantDir() / variant_dir sounds like a better solution... But if I place the Program() builder inside the SConscript: Import('env') env.Program('foo.c') How can I export different environments to the same SConscript file? opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') SConscript('SConscript', 'opt', variant_dir='release') #'opt' --> 'env'??? SConscript('SConscript', 'dbg', variant_dir='debug') #'dbg' --> 'env'??? Unfortunately the discussion in the SCons Wiki does not bring more insight to this topic. Thanks for your input!

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  • What is the cost in bytes for the overhead of a sql_variant column in SQL Server?

    - by Elan
    I have a table, which contains many columns of float data type with 15 digit precision. Each column consumes 8 bytes of storage. Most of the time the data does not require this amount of precision and could be stored as a real data type. In many cases the value can be 0, in which case I could get away with storing a single byte. My goal here is to optimize space storage requirements, which is an issue I am facing working with a SQL Express 4GB database size limit. If byte, real and float data types are stored in a sql_variant column there is obviously some overhead involved in storing these values. What is the cost of this overhead? I would then need to evaluate whether I would actually end up in significant space savings (or not) switching to using sql_variant column data types. Thanks, Elan

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  • Cast object as OleVariant in Delphi

    - by Alan Clark
    Is there a way to pass a wrap and unwrap a TObject descendent in an OleVariant? I am trying to pass a TObject across automation objects. I know it's not a good idea but I don't have a good alternative. Something like this: function GetMyObjAsVariant; var MyObj: TMyObj; begin MyObj := TMyObj.Create; result := OleVariant(MyObj); end; Which would be used by a client as var MyObj: TMyObj; begin MyObj := GetMyObjAsVariant as TMyObj; end; This fails to compile, returning E2015 Operator not applicable to this operand type.

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  • Can Ubuntu be installed in a subdirectory of another Linux variant?

    - by Reid
    I have access to (but not root on) a compute server which is running a Linux distribution that is a few years old. I'd much prefer to use a current Debian-like flavor. Thus, I'm wondering if it is possible to install Ubuntu (or stock Debian) in one of my directories, and use the Ubuntu programs and libraries in preference to what comes with the server. I would need to access arbitrary parts of the server's filesystem, not just the parts under the Ubuntu install. I log in by SSH, so there's no desktop environment needed. But, I would like to be able to use X programs.

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  • How to free member (i.e BSTR, SAFEARRAY, VARIANT) of an IDL User Defined Structure which is encapsul

    - by Picaro De Vosio
    Hi, I have a structure defined in IDL. This structure has following members: { BSTR m_sFirst; BSTR m_sSecond; VARIANT m_vChildStruct; //This member encapsulate a sub structure SAFEARRAY __RPC_FAR * m_saArray; }CustomINFO; I am allocating the memory for the structs using CoTaskMemAlloc and encapsulating it in Variant as follows: vV-vt = VT_RECORD; vV-pvRecord = pStruct; //Pointer of sturct vV-pRecInfo = pRI; //RecordInfo Interface Is it enough to call VariantClear to deallocate the memory of struct and its members? Will it also release the IRecordInfo interface? Or i have to manually get the encapsulated struct and deallocate each member myself and then use CoTaskMemFree to deallocate sturct. Thanks Picaro De Vosio

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  • C# - calling ext. DLL function containing Delphi "variant record" parameter

    - by CaldonCZE
    Hello, In external (Delphi-created) DLL I've got the following function that I need to call from C# application. function ReadMsg(handle: longword; var Msg: TRxMsg): longword; stdcall; external 'MyDll.dll' name 'ReadMsg'; The "TRxMsg" type is variant record, defined as follows: TRxMsg = record case TypeMsg: byte of 1: (accept, mask: longword); 2: (SN: string[6]); 3: (rx_rate, tx_rate: word); 4: (rx_status, tx_status, ctl0, ctl1, rflg: byte); end; In order to call the function from C#, I declared auxiliary structure "my9Bytes" containing array of bytes and defined that it should be marshalled as 9 bytes long array (which is exactly the size of the Delphi record). private struct my9Bytes { [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.U1, SizeConst = 9)] public byte[] data; } Then I declared the imported "ReadMsg" function, using the "my9bytes" struct. [DllImport("MyDll.dll")] private static extern uint ReadMsg(uint handle, ref my9Bytes myMsg); I can call the function with no problem... Then I need to create structure corresponding to the original "TRxMsg" variant record and convert my auxiliary "myMsg" array into this structure. I don't know any C# equivalent of Delphi variant array, so I used inheritance and created the following classes. public abstract class TRxMsg { public byte typeMsg; } public class TRxMsgAcceptMask:TRxMsg { public uint accept, mask; //... } public class TRxMsgSN:TRxMsg { public string SN; //... } public class TRxMsgMRate:TRxMsg { public ushort rx_rate, tx_rate; //... } public class TRxMsgStatus:TRxMsg { public byte rx_status, tx_status, ctl0, ctl1, rflg; //... } Finally I create the appropriate object and initialize it with values manually converted from "myMsg" array (I used BitConverter for this). This does work fine, this solution seems to me a little too complicated, and that it should be possible to do this somehow more directly, without the auxiliary "my9bytes" structures or the inheritance and manual converting of individual values. So I'd like to ask you for a suggestions for the best way to do this. Thanks a lot!

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  • Swiftfox(A variant of Firefox i.e getswiftfox.com ) is taking ages to load in Debian Lenny.

    - by unixbhaskar
    As I mentioned the problem in the Title line..so no stating here once more.I have been using swiftfox for all other partition os without any problem i.e it works flawlessly on Arch,Fedora,Gentoo( my other OSes) ..but giving trouble in Debian Lenny.... Not yet find any clue. Please throw some light on it.The point is that I have had periodically prune swiftfox/firefox internal database; as well as upgrade and update empirically . I am bemused with this problem in Debian Lenny. Cheers! Bhaskar

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  • ref and out parameters in C# and cannot be marked as variant.

    - by Water Cooler v2
    What does the statement mean? From here ref and out parameters in C# and cannot be marked as variant. 1) Does it mean that the following can not be done. public class SomeClass<R, A>: IVariant<R, A> { public virtual R DoSomething( ref A args ) { return null; } } 2) Or does it mean I cannot have the following. public delegate R Reader<out R, in A>(A arg, string s); public static void AssignReadFromPeonMethodToDelegate(ref Reader<object, Peon> pReader) { pReader = ReadFromPeon; } static object ReadFromPeon(Peon p, string propertyName) { return p.GetType().GetField(propertyName).GetValue(p); } static Reader<object, Peon> pReader; static void Main(string[] args) { AssignReadFromPeonMethodToDelegate(ref pReader); bCanReadWrite = (bool)pReader(peon, "CanReadWrite"); Console.WriteLine("Press any key to quit..."); Console.ReadKey(); } I tried (2) and it worked.

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  • Java vs. C variant for desktop and tablet development

    - by MirroredFate
    I am going to write a desktop application, but I am conflicted concerning which language to use. It (the desktop application) will need to have a good GUI, and to be extendable (hopefully good with modules of some sort). It must be completely cross-platform, including executable in various tablet environments. I put this as a requirement while realizing that some modification will no doubt be necessary. The language should also have some form of networking tools available. I have read http://introcs.cs.princeton.edu/java/faq/c2java.html and understand the differences between Java and C very well. I am looking not necessarily at C, but more at a C variant. If it is a complete toss-up, I will use Java as I know Java much better. However, I do not want to use a language that will be inferior for the task I wish to accomplish. Thank you for all suggestions and explanations. NOTE: If this is not the correct stack for this question, I apologize. It seemed appropriate according to the rules.

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  • which style of member-access is preferable

    - by itwasntpete
    the purpose of oop using classes is to encapsulate members from the outer space. i always read that accessing members should be done by methods. for example: template<typename T> class foo_1 { T state_; public: // following below }; the most common doing that by my professor was to have a get and set method. // variant 1 T const& getState() { return state_; } void setState(T const& v) { state_ = v; } or like this: // variant 2 // in my opinion it is easier to read T const& state() { return state_; } void state(T const& v) { state_ = v; } assume the state_ is a variable, which is checked periodically and there is no need to ensure the value (state) is consistent. Is there any disadvantage of accessing the state by reference? for example: // variant 3 // do it by reference T& state() { return state_; } or even directly, if I declare the variable as public. template<typename T> class foo { public: // variant 4 T state; }; In variant 4 I could even ensure consistence by using c++11 atomic. So my question is, which one should I prefer?, Is there any coding standard which would decline one of these pattern? for some code see here

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  • Multiple (variant) arguments overloading in Java: What's the purpose?

    - by fortran
    Browsing google's guava collect library code, I've found the following: // Casting to any type is safe because the list will never hold any elements. @SuppressWarnings("unchecked") public static <E> ImmutableList<E> of() { return (ImmutableList<E>) EmptyImmutableList.INSTANCE; } public static <E> ImmutableList<E> of(E element) { return new SingletonImmutableList<E>(element); } public static <E> ImmutableList<E> of(E e1, E e2) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) { return new RegularImmutableList<E>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8, e9)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList( e1, e2, e3, e4, e5, e6, e7, e8, e9, e10)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList( e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11)); } public static <E> ImmutableList<E> of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11, E e12, E... others) { final int paramCount = 12; Object[] array = new Object[paramCount + others.length]; arrayCopy(array, 0, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12); arrayCopy(array, paramCount, others); return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(array)); } And although it seems reasonable to have overloads for empty and single arguments (as they are going to use special instances), I cannot see the reason behind having all the others, when just the last one (with two fixed arguments plus the variable argument instead the dozen) seems to be enough. As I'm writing, one explanation that pops into my head is that the API pre-dates Java 1.5; and although the signatures would be source-level compatible, the binary interface would differ. Isn't it?

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  • How do I determine darker or lighter color variant of a given color?

    - by Nidonocu
    Given a source color of any hue by the system or user, I'd like a simple algorithm I can use to work out a lighter or darker variants of the selected color. Similar to effects used on Windows Live Messenger for styling the user interface. Language is C# with .net 3.5. Responding to comment: Color format is (Alpha)RGB. With values as bytes or floats. Marking answer: For the context of my use (a few simple UI effects), the answer I'm marking as accepted is actually the most simple for this context. However, I've given up votes to the more complex and accurate answers too. Anyone doing more advanced color operations and finding this thread in future should definitely check those out. Thanks SO. :)

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