security - Difference between CRC and hash method (MD5, SHA1) -

-

both crc , hash methods can used verify integrity of original data. why systems uses hash method nowadays?

crc designed prevent transmission errors, not malicious action.

therefore, isn't collision resistant.

in particular, linear properties of crc codes allow attacker modify message in such way leave check value unchanged


Comments

Post a Comment

Popular posts from this blog

c# - Is it possible to remove an existing registration from Autofac container builder? -

-
something along lines: builder.registertype<mytype>().as<itype>(); builder.registertype<mytype2>().as<itype>(); builder.deregistertype<mytype>().as<itype>() var container = builder.build(); var types = container.resolve<ienumerable<itype>>(); assert.istrue(types.count == 1); assert.istrue(types[0].gettype == typeof(mytype2)); scenario: go through bunch of assemblies , go register types want make sure have 1 implementation of given type. need before create container. track on own nice if autofac me bit. this cannot done directly using containerbuilder , unless start on new one. mind you, having first built container should able construct new container filtering away unwanted types , reusing registrations first container. this: ... var container = builder.build(); builder = new containerbuilder(); var components = container.componentregistry.registrations .where(cr => cr.activator.limittype != typ...
Read more

php - Mysql PK and FK char(36) vs int(10) -

-
i have read mysql can handle indexes , searches better if tables keys integers rather char(36) uuid's. is worth converting int(10)? note: use 1 server , have have plans use multiple databases concurrently therefore removing 1 of big reasons using uuid. our tables innodb if makes difference. thanks in advance. usually rdbms can handle integer keys pk more efficient, other datatypes. reason how build index column, yes: long dont require string (or other typed) keys, should use integers. however: char(36) , int(10) far away being equal, because int(10) much smaller, char(36). dont know, if require many different keys, should keep in mind. update, complete last paragraph: int(10) 32-bit, char(36) 36 - ^byte^ (= 288-bit). not mean, int consumes less space, means, char(36) has 4 times more different keys.
Read more

c++ - Warning : overflow in implicit constant conversion -

-
in following program, line 5 give overflow warning expected, surprisingly line 4 doesn't give warning in gcc: http://www.ideone.com/u0bxn int main() { int = 256; char c1 = i; //line 4 char c2 = 256; //line 5 return 0; } i thinking both lines should give overflow warning. or there i'm missing? the topic led me experiment this: typedef type checking? there said following(which deleted answer, because when run it, didn't show had expected): //however, you'll warning case: typedef int t1; typedef char t2; t1 x = 256; t2 y = x; //possible overflow warning! (but doesn't give warning :() -wall doesn't include many options. -wconversion 1 of them , warns behavior you're interested in. see http://gcc.gnu.org/onlinedocs/gcc/warning-options.html
Read more