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  • Creating 3DES key from bytes

    - by AO
    I create a triple DES key from the a byte array ("skBytes") but when calling getEncoded on the triple DES key ("sk") and comparing it to the byte array, they differ! They are almost the same if you look at the console output, though. How would I create a triple DES key that is exactly as "skBytes"? byte[] skBytes = {(byte) 0x41, (byte) 0x0B, (byte) 0xF0, (byte) 0x9B, (byte) 0xBC, (byte) 0x0E, (byte) 0xC9, (byte) 0x4A, (byte) 0xB5, (byte) 0xCE, (byte) 0x0B, (byte) 0xEA, (byte) 0x05, (byte) 0xEF, (byte) 0x52, (byte) 0x31, (byte) 0xD7, (byte) 0xEC, (byte) 0x2E, (byte) 0x75, (byte) 0xC3, (byte) 0x1D, (byte) 0x3E, (byte) 0x61}; DESedeKeySpec keySpec = new DESedeKeySpec(skBytes); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DESede"); SecretKey sk = keyFactory.generateSecret(keySpec); for(int i = 0; i < skBytes.length; i++) { System.out.println("(sk.getEncoded()[i], skBytes[i]) = (" + sk.getEncoded()[i] +", " + skBytes[i] + ")"); } Console output: (sk.getEncoded()[i], skBytes[i]) = (64, 65) (sk.getEncoded()[i], skBytes[i]) = (11, 11) (sk.getEncoded()[i], skBytes[i]) = (-15, -16) (sk.getEncoded()[i], skBytes[i]) = (-101, -101) (sk.getEncoded()[i], skBytes[i]) = (-68, -68) (sk.getEncoded()[i], skBytes[i]) = (14, 14) (sk.getEncoded()[i], skBytes[i]) = (-56, -55) (sk.getEncoded()[i], skBytes[i]) = (74, 74) (sk.getEncoded()[i], skBytes[i]) = (-75, -75) (sk.getEncoded()[i], skBytes[i]) = (-50, -50) (sk.getEncoded()[i], skBytes[i]) = (11, 11) (sk.getEncoded()[i], skBytes[i]) = (-22, -22) (sk.getEncoded()[i], skBytes[i]) = (4, 5) (sk.getEncoded()[i], skBytes[i]) = (-17, -17) (sk.getEncoded()[i], skBytes[i]) = (82, 82) (sk.getEncoded()[i], skBytes[i]) = (49, 49) (sk.getEncoded()[i], skBytes[i]) = (-42, -41) (sk.getEncoded()[i], skBytes[i]) = (-20, -20) (sk.getEncoded()[i], skBytes[i]) = (47, 46) (sk.getEncoded()[i], skBytes[i]) = (117, 117) (sk.getEncoded()[i], skBytes[i]) = (-62, -61) (sk.getEncoded()[i], skBytes[i]) = (28, 29) (sk.getEncoded()[i], skBytes[i]) = (62, 62) (sk.getEncoded()[i], skBytes[i]) = (97, 97)

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  • Insert MANY key value pairs fast into berkeley db with hash access

    - by Kungi
    Hi, i'm trying to build a hash with berkeley db, which shall contain many tuples (approx 18GB of key value pairs), but in all my tests the performance of the insert operations degrades drastically over time. I've written this script to test the performance: #include<iostream> #include<db_cxx.h> #include<ctime> #define MILLION 1000000 int main () { long long a = 0; long long b = 0; int passes = 0; int i = 0; u_int32_t flags = DB_CREATE; Db* dbp = new Db(NULL,0); dbp->set_cachesize( 0, 1024 * 1024 * 1024, 1 ); int ret = dbp->open( NULL, "test.db", NULL, DB_HASH, flags, 0); time_t time1 = time(NULL); while ( passes < 100 ) { while( i < MILLION ) { Dbt key( &a, sizeof(long long) ); Dbt data( &b, sizeof(long long) ); dbp->put( NULL, &key, &data, 0); a++; b++; i++; } DbEnv* dbep = dbp->get_env(); int tmp; dbep->memp_trickle( 50, &tmp ); i=0; passes++; std::cout << "Inserted one million --> pass: " << passes << " took: " << time(NULL) - time1 << "sec" << std::endl; time1 = time(NULL); } } Perhaps you can tell me why after some time the "put" operation takes increasingly longer and maybe how to fix this. Thanks for your help, Andreas

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  • Authentication using cookie key with asynchronous callback

    - by greg
    I need to write authentication function with asynchronous callback from remote Auth API. Simple authentication with login is working well, but authorization with cookie key, does not work. It should checks if in cookies present key "lp_login", fetch API url like async and execute on_response function. The code almost works, but I see two problems. First, in on_response function I need to setup secure cookie for authorized user on every page. In code user_id returns correct ID, but line: self.set_secure_cookie("user", user_id) does't work. Why it can be? And second problem. During async fetch API url, user's page has loaded before on_response setup cookie with key "user" and the page will has an unauthorized section with link to login or sign on. It will be confusing for users. To solve it, I can stop loading page for user who trying to load first page of site. Is it possible to do and how? Maybe the problem has more correct way to solve it? class BaseHandler(tornado.web.RequestHandler): @tornado.web.asynchronous def get_current_user(self): user_id = self.get_secure_cookie("user") user_cookie = self.get_cookie("lp_login") if user_id: self.set_secure_cookie("user", user_id) return Author.objects.get(id=int(user_id)) elif user_cookie: url = urlparse("http://%s" % self.request.host) domain = url.netloc.split(":")[0] try: username, hashed_password = urllib.unquote(user_cookie).rsplit(',',1) except ValueError: # check against malicious clients return None else: url = "http://%s%s%s/%s/" % (domain, "/api/user/username/", username, hashed_password) http = tornado.httpclient.AsyncHTTPClient() http.fetch(url, callback=self.async_callback(self.on_response)) else: return None def on_response(self, response): answer = tornado.escape.json_decode(response.body) username = answer['username'] if answer["has_valid_credentials"]: author = Author.objects.get(email=answer["email"]) user_id = str(author.id) print user_id # It returns needed id self.set_secure_cookie("user", user_id) # but session can's setup

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  • Database design and foreign keys: Where should they be added in related tables?

    - by Carvell Fenton
    I have a relatively simple subset of tables in my database for tracking something called sessions. These are academic sessions (think offerings of a particular program). The tables to represent a sessions information are: sessions session_terms session_subjects session_mark_item_info session_marks All of these tables have their own primary keys, and are like a tree, in that sessions have terms, terms have subjects, subjects have mark items, etc. So each on would have at least its "parent's" foreign key. My question is, design wise is it a good idea to include the sessions primary key in the other tables as a foreign key to easily select related session items, or is that too much redundency? If I include the session foreign key (or all parent foreign keys from tables up the heirarchy) in all the tables, I can easily select all the marks for a session. As an example, something like SELECT mark FROM session_marks WHERE sessionID=... If I don't, then I would have to combine selects with something like WHERE something IN (SELECT... Which approach is "more correct" or efficient? Thanks in advance!

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  • NHibernate bag is always null

    - by Neville Chinan
    I have set up my mapping file and classes as suggested by many articles class A { ... IList BBag {get;set;} ... } class B { ... A aObject {get;set;} ... } <class name="A">...<bag name="BBag" table="B" inverse="true" lazy="false"><key column="A_ID" /><one-to-many class="B" /></bag>... <class name="B">...<many-to-one name="aObject" class="A" column="A_ID" />... I added a set of A's to the A table and a set of B's to the B table, all the data is stored as expected. However if I try and access aInstance.BBag.Count I get a null reference exception. I think I missing some key knowledge on how an bag gets instantiated. Thanks

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  • Fastest way to modify a decimal-keyed table in MySQL?

    - by javanix
    I am dealing with a MySQL table here that is keyed in a somewhat unfortunate way. Instead of using an auto increment table as a key, it uses a column of decimals to preserve order (presumably so its not too difficult to insert new rows while preserving a primary key and order). Before I go through and redo this table to something more sane, I need to figure out how to rekey it without breaking everything. What I would like to do is something that takes a list of doubles (the current keys) and outputs a list of integers (which can be cast down to doubles for rekeying). For example, input {1.00, 2.00, 2.50, 2.60, 3.00} would give output {1, 2, 3, 4, 5). Since this is a database, I also need to be able to update the rows nicely: UPDATE table SET `key`='3.00' WHERE `key`='2.50'; Can anyone think of a speedy algorithm to do this? My current thought is to read all of the doubles into a vector, take the size of the vector, and output a new vector with values from 1 => doubleVector.size. This seems pretty slow, since you wouldn't want to read every value into the vector if, for instance, only the last n/100 elements needed to be modified. I think there is probably something I can do in place, since only values after the first non-integer double need to be modified, but I can't for the life of me figure anything out that would let me update in place as well. For instance, setting 2.60 to 3.00 the first time you see 2.50 in the original key list would result in an error, since the key value 3.00 is already used for the table.

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  • Fastest way to convert a list of doubles to a unique list of integers?

    - by javanix
    I am dealing with a MySQL table here that is keyed in a somewhat unfortunate way. Instead of using an auto increment table as a key, it uses a column of decimals to preserve order (presumably so its not too difficult to insert new rows while preserving a primary key and order). Before I go through and redo this table to something more sane, I need to figure out how to rekey it without breaking everything. What I would like to do is something that takes a list of doubles (the current keys) and outputs a list of integers (which can be cast down to doubles for rekeying). For example, input {1.00, 2.00, 2.50, 2.60, 3.00} would give output {1, 2, 3, 4, 5). Since this is a database, I also need to be able to update the rows nicely: UPDATE table SET `key`='3.00' WHERE `key`='2.50'; Can anyone think of a speedy algorithm to do this? My current thought is to read all of the doubles into a vector, take the size of the vector, and output a new vector with values from 1 => doubleVector.size. This seems pretty slow, since you wouldn't want to read every value into the vector if, for instance, only the last n/100 elements needed to be modified. I think there is probably something I can do in place, since only values after the first non-integer double need to be modified, but I can't for the life of me figure anything out that would let me update in place as well. For instance, setting 2.60 to 3.00 the first time you see 2.50 in the original key list would result in an error, since the key value 3.00 is already used for the table.

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  • SQL Server problems reading columns with a foreign key

    - by illdev
    I have a weird situation, where simple queries seem to never finish for instance SELECT top 100 ArticleID FROM Article WHERE ProductGroupID=379114 returns immediately SELECT top 1000 ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT top 1000 ArticleID FROM Article returns immediately By 'returning' I mean 'in query analyzer the green check mark appears and it says "Query executed successfully"'. I sometimes get the rows painted to the grid in qa, but still the query goes on waiting for my client to time out - 'sometimes': SELECT ProductGroupID AS Product23_1_, ArticleID AS ArticleID1_, ArticleID AS ArticleID18_0_, Inventory_Name AS Inventory3_18_0_, Inventory_UnitOfMeasure AS Inventory4_18_0_, BusinessKey AS Business5_18_0_, Name AS Name18_0_, ServesPeople AS ServesPe7_18_0_, InStock AS InStock18_0_, Description AS Descript9_18_0_, Description2 AS Descrip10_18_0_, TechnicalData AS Technic11_18_0_, IsDiscontinued AS IsDisco12_18_0_, Release AS Release18_0_, Classifications AS Classif14_18_0_, DistributorName AS Distrib15_18_0_, DistributorProductCode AS Distrib16_18_0_, Options AS Options18_0_, IsPromoted AS IsPromoted18_0_, IsBulkyFreight AS IsBulky19_18_0_, IsBackOrderOnly AS IsBackO20_18_0_, Price AS Price18_0_, Weight AS Weight18_0_, ProductGroupID AS Product23_18_0_, ConversationID AS Convers24_18_0_, DistributorID AS Distrib25_18_0_, type AS Type18_0_ FROM Article AS articles0_ WHERE (IsDiscontinued = '0') AND (ProductGroupID = 379121) shows this behavior. I have no idea what is going on. Probably select is broken ;) I got a foreign key on ProductGroups ALTER TABLE [dbo].[Article] WITH CHECK ADD CONSTRAINT [FK_ProductGroup_Articles] FOREIGN KEY([ProductGroupID]) REFERENCES [dbo].[ProductGroup] ([ProductGroupID]) GO ALTER TABLE [dbo].[Article] CHECK CONSTRAINT [FK_ProductGroup_Articles] there are some 6000 rows and IsDiscontinued is a bit, not null, but leaving this condition out does not change the outcome. Anyone can tell me how to handle such a situation? More info, anyone? Additional Info: this does not seem to be restricted to this Foreign Key, but all/some referencing this entity.

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  • What is the corrrect way to increment a field making up part of a composit key

    - by Tr1stan
    I have a bunch of tables whose primary key is made up of the foreign keys of other tables (Composite key). Therefore for example the attributes (as a very cut down version) might look like this: A[aPK, SomeFields] 1:M B[bPK, aFK, SomeFields] 1:M C[cPK, bFK, aFK, SomeFields] as data this could look like: A[aPK, SomeFields]: 1, Foo 2, Bar B[bPK, aFK, SomeFields]: 1, 1, FooData1 2, 1, FooData2 1, 2, BarData1 2, 2, BarData2 C[cPK, bFK, aFK, SomeFields]: 1, 1, 1, FooData1More 2, 1, 1, FooData1More 1, 2, 1, FooData2More 2, 2, 1, FooData2More 1, 1, 2, BarData1More 2, 1, 2, BarData1More 1, 2, 2, BarData2More 2, 2, 2, BarData2More I've got this running in a MSSQL DBMS and I'm looking for the best way to increment the left most column, in each table when a new tuple is added to it. I can't use the Auto Increment Identity Specification option as that has no idea that it is part of a composite key. I also don't want to use any aggregate function such as: MAX(field)+1 as this will have adverse affects with multiple users inputting data, rolling back etc. There might however be a nice trigger based option here, but I'm not sure. This must be a common issue so I'm hoping that someone has a lovely solution. As a side which may or may not affect the answer, I'm using Entity Framework 1.0 as my ORM, within a c# MVC application.

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  • NHibernate One to One Foreign Key ON DELETE CASCADE

    - by xll
    I need to implement One-to-one association between Project and ProjecSettings using fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Id(x => x.Id) .UniqueKey(MapUtils.Col<Project>(x => x.Id)) .GeneratedBy.HiLo("NHHiLoIdentity", "NextHiValue", "1000", string.Format("[EntityName] = '[{0}]'", MapUtils.Table<Project>())) .Not.Nullable(); HasOne(x => x.ProjectSettings) .PropertyRef(x => x.Project); } } public class ProjectSettingsMap : ClassMap<ProjectSettings> { public ProjectSettingsMap() { Id(x => x.Id) .UniqueKey(MapUtils.Col<ProjectSettings>(x => x.Id)) .GeneratedBy.HiLo("NHHiLoIdentity", "NextHiValue", "1000", string.Format("[EntityName] = '[{0}]'", MapUtils.Table<ProjectSettings>())); References(x => x.Project) .Column(MapUtils.Ref<ProjectSettings, Project>(p => p.Project, p => p.Id)) .Unique() .Not.Nullable(); } } This results in the following sql for Project Settings: CREATE TABLE ProjectSettings ( Id bigint PRIMARY KEY NOT NULL, Project_Project_Id bigint NOT NULL UNIQUE, /* Foreign keys */ FOREIGN KEY (Project_Project_Id) REFERENCES Project() ON DELETE NO ACTION ON UPDATE NO ACTION ); What I am trying to achieve is to have ON DELETE CASCADE for the FOREIGN KEY (Project_Project_Id), so that when the project is deleted through sql query, it's settings are deleted too. How can I achieve this ? EDIT: I know about Cascade.Delete() option, but it's not what I need. Is there any way to intercept the FK statement generation?

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  • How to configure SHIFT+LEFT, SHIFT+RIGHT, SHIFT+HOME and SHIFT+END keys in terminal on Mac?

    - by Misha Moroshko
    To configure the Home and End keys in terminal on MacBook Air (OS X 10.7.2) I defined in Terminal -> Preferences -> Keyboard: Key Action ---- ------ Home \033OH End \033OF What are the codes to configure the following combinations so that they will work like in Windows? Shift+Left (should select the character on the left) Shift+Right (should select the character on the right) Shift+Home (should select all the characters on the left) Shift+End (should select all the characters on the right)

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  • A GUID as the MySQL table's Primary Key or as a separate column

    - by Ben
    I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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  • Fetching just the Key/id from a ReferenceProperty in App Engine

    - by ozone
    Hi SO, I could use a little help in AppEngine land... Using the [Python] API I create relationships like this example from the docs: class Author(db.Model): name = db.StringProperty() class Story(db.Model): author = db.ReferenceProperty(Author) story = db.get(story_key) author_name = story.author.name As I understand it, that example will make two datastore queries. One to fetch the Story and then one to deference the Author inorder to access the name. But I want to be able to fetch the id, so do something like: story = db.get(story_key) author_id = story.author.key().id() I want to just get the id from the reference. I do not want to have to deference (therefore query the datastore) the ReferenceProperty value. From reading the documentation it says that the value of a ReferenceProperty is a Key Which leads me to think that I could just call .id() on the reference's value. But it also says: The ReferenceProperty model provides features for Key property values such as automatic dereferencing. I can't find anything that explains when this referencing takes place? Is it safe to call .id() on the ReferenceProperty's value? Can it be assumed that calling .id() will not cause a datastore lookup?

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  • Parent-Child relation while using object data source

    - by Saba
    Hello guys I am experiencing with a class generator I've written, which generates a class for each table in database with each table field as a property and such. Before that, I used to add a typed dataset to the project and add some tables to it. It automatically detected the relationship between tables and when I added a parent table as data source of a datagrid, I could add another datagrid and use the foreing key data member of it's bindingsource to fill it, and when someone moved the focus on parent datagrid, the data in child datagrid would change accordingly. Now that I have my classes, I add an object as data source for my 2 datagrids, but obviously it doesn't detect a parent child relation. But It'd really help if I could have that foreign key relation in my object datasources. Is there any way to have that relation in object datasource?

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  • Dictionaries with more than one key per value in Python

    - by nickname
    I am attempting to create a nice interface to access a data set where each value has several possible keys. For example, suppose that I have both a number and a name for each value in the data set. I want to be able to access each value using either the number OR the name. I have considered several possible implementations: Using two separate dictionaries, one for the data values organized by number, and one for the data values organized by name. Simply assigning two keys to the same value in a dictionary. Creating dictionaries mapping each name to the corresponding number, and vice versa Attempting to create a hash function that maps each name to a number, etc. (related to the above) Creating an object to encapsulate all three pieces of data, then using one key to map dictionary keys to the objects and simply searching the dictionary to map the other key to the object. None of these seem ideal. The first seems ugly and unmaintainable. The second also seems fragile. The third/fourth seem plausible, but seem to require either much manual specification or an overly complex implementation. Finally, the fifth loses constant-time performance for one of the lookups. In C/C++, I believe that I would use pointers to reference the same piece of data from different keys. I know that the problem is rather similar to a database lookup problem by a non-key column, however, I would like (if possible), to maintain the approximate O(1) performance of Python dictionaries. What is the most Pythonic way to achieve this data structure?

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  • INSERT..ON DUPLICATE KEY UPDATE - but NOT using the duplicate key to compare.

    - by calumbrodie
    I am trying to solve a problem I have inherited with poor treatment of different data sources. I have a user table that contains BOTH good and evil users. create table `users`( `user_id` int(13) NOT NULL AUTO_INCREMENT , `email` varchar(255) , `name` varchar(255) , PRIMARY KEY (`user_id`) ); In this table the primary key is currently set to be user_id. I have another table ('users_evil') which contains ONLY the evil users (all the users from this table are included in the first table) - the user_id's on this table do NOT correspond to those in the first table. I want to have all my users in one table, and simply flag which are good and which are evil. What I want to do is alter the user table and add a column ('evil') which defaults to 0. I then want to dump the data from my 'users_evil') table and then run an INSERT..ON DUPLICATE KEY UPDATE with this data into the first table (setting 'evil'=1 where the emails match) The problem is that the 'PK' is set to the user_id and not the 'email'. Any suggestions, or even another strategy to successfully achive this. Can I run this statement but treat another column as PK only for the duration of the statement.

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  • assign characters to key combinations in XP or Visual Studio .Net

    - by cpj
    I'm running Mac OSX on a MacBookPro (UK keyboard). I run windows XP under parallels in a VM. I run Visual Studio .Net 2003 and 2008 in XP in the VM when i need to. I have English United Kingdom and English United states keyboards setup in XP. (they switch sometimes for no apparent reason) There is no hash "#" key on my mac's keyboard. However, in OSX I can get a hash with an alt+3 key combination. But In Windows XP... I can not make a "#" character. I can go to the character map in windows and copy a hash.. switch into OSX and copy a hash.. search in code and copy a hash.. but I can not make a hash in XP using my keyboard without typing U+0023: ... which you can imagine is annoying. coding anything with hash symbols is becoming a choir. Anyone got any advice or key mapping tricks I can use to get hash characters working in XP using my mac UK keyboard?

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  • Restricting deletion with NHibernate

    - by FrontSvin
    I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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  • Updating a composite primary key

    - by VBCSharp
    I am struggling with the philosophical discussions about whether or not to use composite primary keys on my SQL Server database. I have always used the surrogate keys in the past and I am challenging myself by leaving my comfort zone to try something different. I have read many discussion but can't come to any kind of solution yet. The struggle I am having is when I have to update a record with the composite PK. For example, the record in questions is like this: ContactID, RoleID, EffectiveDate, TerminationDT. The PK in this case is the ContactID, RoleID, and EffectiveDate. TerminationDT can be null. If in my UI, the user changes the RoleID and then I need to update the record. Using the surrogate key I can do an Update Table Set RoleID = 1 WHERE surrogateID = Z. However, using the Composite Key way, once one of the fields in the composite key changes I have no way to reference the old record to update it without now maintaining somewhere in the UI a reference to the old values. I do not bind datasources in my UI. I open a connection, get the data and store it in a bucket, then close the connection. What are everyone's opinions? Thanks.

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  • Handling primary key duplicates in a data warehouse load

    - by Meff
    I'm currently building an ETL system to load a data warehouse from a transactional system. The grain of my fact table is the transaction level. In order to ensure I don't load duplicate rows I've put a primary key on the fact table, which is the transaction ID. I've encountered a problem with transactions being reversed - In the transactional database this is done via a status, which I pick up and I can work out if the transaction is being done, or rolled back so I can load a reversal row in the warehouse. However, the reversal row will have the same transaction ID and so I get a primary key violation. I've solved this for now by negating the primary key, so transaction ID 1 would be a payment, and transaction ID -1 (In the warehouse only) would be the reversal. I have considered an alternative of generating a BIT column, where 0 is normal and 1 is reversal, then making the PK the transaction ID and the BIT column. My question is, is this a good practice, and has anyone else encountered anything like this? For reference, this is a payment processing system, so values will not be modified, so there will only ever be transactions and reversals.

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  • Why can't we just use a hash of passphrase as the encryption key (and IV) with symmetric encryption algorithms?

    - by TX_
    Inspired by my previous question, now I have a very interesting idea: Do you really ever need to use Rfc2898DeriveBytes or similar classes to "securely derive" the encryption key and initialization vector from the passphrase string, or will just a simple hash of that string work equally well as a key/IV, when encrypting the data with symmetric algorithm (e.g. AES, DES, etc.)? I see tons of AES encryption code snippets, where Rfc2898DeriveBytes class is used to derive the encryption key and initialization vector (IV) from the password string. It is assumed that one should use a random salt and a shitload of iterations to derive secure enough key/IV for the encryption. While deriving bytes from password string using this method is quite useful in some scenarios, I think that's not applicable when encrypting data with symmetric algorithms! Here is why: using salt makes sense when there is a possibility to build precalculated rainbow tables, and when attacker gets his hands on hash he looks up the original password as a result. But... with symmetric data encryption, I think this is not required, as the hash of password string, or the encryption key, is never stored anywhere. So, if we just get the SHA1 hash of password, and use it as the encryption key/IV, isn't that going to be equally secure? What is the purpose of using Rfc2898DeriveBytes class to generate key/IV from password string (which is a very very performance-intensive operation), when we could just use a SHA1 (or any other) hash of that password? Hash would result in random bit distribution in a key (as opposed to using string bytes directly). And attacker would have to brute-force the whole range of key (e.g. if key length is 256bit he would have to try 2^256 combinations) anyway. So either I'm wrong in a dangerous way, or all those samples of AES encryption (including many upvoted answers here at SO), etc. that use Rfc2898DeriveBytes method to generate encryption key and IV are just wrong.

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  • How to generate Serial Keys? [closed]

    - by vincent mathew
    Which software can I use to generate Product keys if I have the GroupId, KeyId, Secret and Hash for the generation? Edit: I had seen a post which generated Product Keys using this information. [Additional Key Details/Activation Decryption*: GroupId = 86f 2159 KeyId = ed46 60742 Secret = e0cdc320ba048 3954789545910344 Hash = 5f 95 ] So I was wondering if there is any software which could generate keys using this information? Thanks.

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  • MYSQL how to sum rows with same key, then delete the duplicate rows

    - by Bhante-S
    What I have: key data 1      22 1       5 2       6 3       1 3      -3 What I want: key data 1      27 2       6 3      -2 I don’t mind doing this with two or more queries, esp. if they are simple--makes for easier maintenance. Also the tables are fairly small (<2,000 records). The ‘key’ field is indexed and allows duplicates. Muchas Gracias

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  • Multiple INET sockets (mulple IP's too) connected to UNIX sockets

    - by Andrew
    HOST = same host all the time, accepts multiple connection. I have a dedicated server and I will buy extra IP's. Socket 1 connects to HOST:PORT, from IP-1 Socket 2 connects to HOST:PORT, from IP-1 Socket 3 connects to HOST:PORT, from IP-1 Socket 4 connects to HOST:PORT, from IP-2 Socket 5 connects to HOST:PORT, from IP-2 Socket 6 connects to HOST:PORT, from IP-2 After creating all sockets I want to access them easy as UNIX sockets from PHP. /sys/socket1 /sys/socket2 /sys/socket3 /sys/socket4 /sys/socket5 /sys/socket6 I want the sockets to work in background (like daemon) and I want to be able to connect from PHP to any of this sockets and RECV/SEND whatever I want. I saw "socat" and I think that's the solution for me, please tell me how to use socat, or how to do it other way. Thankyou!

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