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  • Using Public/Private keys in reverse

    - by Wizzarding
    Hi, I have a situation where I need to make some data available for reading by anyone from a specific device, where the data is pre-loaded on the device, but I cannot allow anyone to create their own device and populate it with their own data in the same format. I know this sounds a little crazy, but there is a good reason! I was planning to use Public Key cryptography, encrypting the data with a public key, but then publishing the private key to anyone who wants to read the data. However, after looking at the RSACryptoServiceProvider and how it works it looks like I cannot just publish the private key as the private key can be used to create the public key. Could someone confirm that suspicion, or give me some hints on how I might be able to make this work! Many Thanks.

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  • GQL Query with __key__ in List of KEYs

    - by bossylobster
    In the GQL reference [1], it is encouraged to use the IN keyword with a list of values, and to construct a Key from hand the GQL query SELECT * FROM MyModel WHERE __key__ = KEY('MyModel', 'my_model_key') will succeed. However, using the code you would expect to work: SELECT * FROM MyModel WHERE __key__ IN (KEY('MyModel', 'my_model_key1'), KEY('MyModel', 'my_model_key2')) in the Datastore Viewer, there is a complaint of "Invalid GQL query string." What is the correct way to format such a query? [1] http://code.google.com/appengine/docs/python/datastore/gqlreference.html PS I know there are more efficient ways to do this in Python (without constructing a GQL query) and using the remote_api, but each call to the remote_api counts against quota. In an environment where quota is not (necessarily) free, quick and dirty queries are very helpful.

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  • Foreign Keys in SQLITE in the Google Gears framework

    - by Maxim Gershkovich
    Hi all, Could someone please tell me why the following foreign key constraint (although executes fine) is not enforced by SQLITE? Could someone pleasse provide an example of how I can go about enforcing the relationship? CREATE TABLE User (UserID TEXT Unique NOT NULL PRIMARY KEY, FirstName TEXT NOT NULL, LastName TEXT NOT NULL, Username TEXT NOT NULL, Password TEXT NOT NULL, Email TEXT NOT NULL, SignupDate TEXT NOT NULL) CREATE TABLE Category (CategoryID TEXT Unique NOT NULL PRIMARY KEY, UserID TEXT, FOREIGN KEY(UserID) REFERENCES User(UserID))

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  • JPA 2.0 Eclipse Link ... Composite primary keys

    - by Parhs
    I have two entities(actually more but it doenst matter) Exam and Exam_Normals Its a oneToMany relationship... The problem is that i need a primary key for Exams_Normals PK (Exam_ID Item) Item should be 1 2 3 4 5 etc.... But cant achieve it getting errors An alternative would be to: I cound use an IDENTITY and a ManyToOne relationship at Exam_Normals but that should be like PK(Exam_Normals_ID) and a reference to Exam and an extra collumn Item to keep an order.. SO 3 collumns But to avoid the alternative tried I tried with @IdClass and got errors Tried @EmbeddedID everything nothing works Any idea??

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  • Basic question about encryption - what exactly are keys?

    - by Tomas
    Hi, I was browsing and found good articles about encryption. However, none of them described why the key lenght is important and what exactly the key is used for. My guess is that could work this way: 0101001101010101010 Key: 01010010101010010101 //the longer the key, the longer unique sequence XOR or smth: //result Is this at least a bit how it works or I am missing something? Thanks

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  • Hyphen in Array keys

    - by Vincent
    All, I have an array with hyphens in the key name. How do I extract the value of it in PHP? It returns a 0 to me, if I access like this: print $testarray->test-key; This is how the array looks like testarray[] = {["test-key"]=2,["hotlink"]=1} Thanks

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  • Meshing different systems of keys together in XML Schema

    - by Tom W
    Hello SO, I'd like to ask people's thoughts on an XSD problem I've been pondering. The system I am trying to model is thus: I have a general type that represents some item in a hypothetical model. The type is abstract and will be inherited by all manner of different model objects, so the model is heterogeneous. Furthermore, some types exist only as children of other types. Objects are to be given an identifier, but the scope of uniqueness of this identifier varies. Some objects - we will call them P (for Parent) objects - must have a globally unique identifier. This is straightforward and can use the xs:key schema element. Other objects (we can call them C objects, for Child) are children of a P object and must have an identifier that is unique only in the scope of that parent. For example, object P1 has two children, object C1 and C2, and object P2 has one child, object C3. In this system, the identifiers given could be as follows: P1: 1 (1st P object globally) P2: 2 (2nd P object globally) C1: 1 (1st C object of P1) C2: 2 (2nd C object of P1) C3: 1 (1st C object of P2) I want the identity syntax of every model object to be identical if possible, therefore my first pass at implementing is to define a single type: <xs:complexType name="ModelElement"> <xs:attribute name="IDMode" type="IdentityMode"/> <xs:attribute name="Identifier" type="xs:string"/> </xs:complexType> where the IdentityMode is an enumerated value: <xs:simpleType name="IdentityMode"> <xs:restriction base="xs:string"> <xs:enumeration value="Identified"/> <xs:enumeration value="Indexed"/> <xs:enumeration value="None"/> </xs:restriction> </xs:simpleType> Here "Identified" signifies a global identifier, and "Indexed" indicates an identifier local only to the parent. My question is, how do I enforce these uniqueness conditions using unique, key or other schema elements based on the IdentityMode property of the given subtype of ModelElement?

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  • SQL Server Composite Primary Keys

    - by Colin
    I am attempting to replace all records for a give day in a certain table. The table has a composite primary key comprised of 7 fields. One such field is date. I have deleted all records which have a date value of 2/8/2010. When I try to then insert records into the table for 2/8/2010, I get a primary key violation. The records I am attempting to insert are only for 2/8/2010. Since date is a component of the PK, shouldn't there be no way to violate the constraint as long as the date I'm inserting is not already in the table? Thanks in advance.

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  • Get Array value by string of keys

    - by Esben Petersen
    Hello, i'm building a template engine for my next project, which is going great. It replaces {tag} with a corresponding value. But, i want {tag[0][key]} to be replaced as well. All i need to know is how to get the value, if i have the string representation of the array and key, like this: $arr = array( 0=>array( 'key'=>'value' ), 1=>array( 'key'=>'value2' ) ); $tag = 'arr[0][key]'; echo($$tag); This is a very simple version of the problem, i hope you understand it. Or else i would be happy to anwser any questions about it :) Thanks for any help in advantage

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  • What's wrong with foreign keys?

    - by kronoz
    I remember hearing Joel mention in the podcast that he'd barely ever used a foreign key (if I remember correctly). However, to me they seem pretty vital to avoid duplication and subsequent data integrity problems throughout your database. Do people have some solid reasons as to why (to avoid a discussion in lines with SO principals)? Edit: "I've yet to have a reason to create a foreign key, so this might be my first reason to actually set up one."

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  • How many keys are too many in memcached?

    - by jack
    I currently have about 650,000 items in memcached (430MB memory used) and the number is still increasing. It's expected to exceed 1,000,000 items before going flat. Current hit/miss ratio is 25:1 so the efficiency is pretty good. I just wanted to ask is one million items in memcached on single server too many? If no, how many is too many?

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  • SQLAlchemy: an efficient/better select by primary keys?

    - by hadrien
    Yet another newbie question.. Let's say I have an user table in declarative mode: class User(Base): __tablename__ = 'user' id = Column(u'id', Integer(), primary_key=True) name = Column(u'name', String(50)) When I have a list of users identifiers, I fetch them from db with: user_ids = [1, 2, 3, 4, 5] users = Session.query(User).filter(User.id.in_(user_ids)).all() I dislike using in_ because I think I learned it has bad performance on indexed fields (is that true/false?). Anyway, is there a better way doing that query? Thanks!

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  • MySQLi String comparisons using keys

    - by asdasd
    I have a table with lets say 2 columns. id number, and value. Value is a string (var char). Lets say i have a number x, and a list of numbers a1, a2, a3, a4, a5..... where x is not in the list. All of these numbers correspond to a unique row in the table. I want to know if the string value for x in the table is contained in one of the string values for any table entry for a1, a2, a3, a4... Lets say i have these rows: x, aaa a1, bbb a2, ccc a3, ddd a4, aaabbbcc then i want somehow a confirmation that yes, the value for x is included in one of the values in my list of numbers (a4 contains x). I know i can do this in a couple queries and shove it down some PHP and get my answer. But can i do this with one query?

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  • NHibernate SchemaUpdate adding existing foreign keys again?

    - by afsharm
    I'm using SchemaUpdate to synchronize my hbms with existing database. Database has recently created based on hbms and is completely up-to-date. But SchemaUpdate generates all foreign key constraints again. For example suppose you have Student and Teacher. Student has association to Teacher with name ArtTeacher. ArtTeacher is a foreign key from Student to Teacher. Suppose database is up-to-date and currently holde Student, Teacher and their foreign key relation. So HBM and Database are equivalent. Know SchemaUpdate must not do anything but when I see its generated scripts, it re-produce that foreign key again. Why this happens? Is there any way to avoid it?

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  • Converting keys of an array/object-tree to lowercase

    - by tstenner
    Im currently optimizing a PHP application and found one function being called around 10-20k times, so I'd thought I'd start optimization there. function keysToLower($obj) { if(!is_object($obj) && !is_array($obj)) return $obj; foreach($obj as $key=>$element) { $element=keysToLower($element); if(is_object($obj)) { $obj->{strtolower($key)}=$element; if(!ctype_lower($key)) unset($obj->{$key}); } else if(is_array($obj) && ctype_upper($key)) { $obj[strtolower($key)]=$element; unset($obj[$key]); } } return $obj; } Most of the time is spent in recursive calls (which are quite slow in PHP), but I don't see any way to convert it to a loop. What would you do?

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  • Foreign keys and NULL in mySQL

    - by Industrial
    Hi everyone, Can I have a column in my values table (value) referenced as a foreign key to knownValues table, and let it be NULL whenever needed, like in the example: Table: values product type value freevalue 0 1 NULL 100 1 2 NULL 25 3 3 1 NULL Table: types id name prefix 0 length cm 1 weight kg 2 fruit NULL Table: knownValues id Type name 0 2 banana Note: The types in the table values & knownValues are of course referenced into the types table. Thanks!

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  • vb.net press/release keys

    - by Cyclone
    How can you simulate keypresses and releases? I know you can essentially hit a key with Sendkeys.SendWait, but how can your code press and hold q, for example? Any help is much appreciated! Everything I find keeps pointing me at sendkeys, which is not correct. I essentially wish to be able to call something like press("q") and release("q"). The effect would be the same as physically holding them down. Thanks for your help!

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  • Joining tables with composite keys in a legacy system in hibernate

    - by Steve N
    Hi, I'm currently trying to create a pair of Hibernate annotated classes to load (read only) from a pair of tables in a legacy system. The legacy system uses a consistent (if somewhat dated) approach to keying tables. The tables I'm attempting to map are as follows: Customer CustomerAddress -------------------------- ---------------------------- customerNumber:string (pk) customerNumber:string (pk_1) name:string sequenceNumber:int (pk_2) street:string postalCode:string I've approached this by creating a CustomerAddress class like this: @Entity @Table(name="CustomerAddress") @IdClass(CustomerAddressKey.class) public class CustomerAddress { @Id @AttributeOverrides({ @AttributeOverride(name = "customerNumber", column = @Column(name="customerNumber")), @AttributeOverride(name = "sequenceNumber", column = @Column(name="sequenceNumber")) }) private String customerNumber; private int sequenceNumber; private String name; private String postalCode; ... } Where the CustomerAddressKey class is a simple Serializable object with the two key fields. The Customer object is then defined as: @Entity @Table(name = "Customer") public class Customer { private String customerNumber; private List<CustomerAddress> addresses = new ArrayList<CustomerAddress>(); private String name; ... } So, my question is: how do I express the OneToMany relationship on the Customer table?

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  • Securing database keys for client-side processing

    - by danp
    I have a tree of information which is sent to the client in a JSON object. In that object, I don't want to have raw IDs which are coming from the database. I thought of making a hash of the id and a field in the object (title, for example) or a salt, but I'm worried that this might have a serious effect on processing overhead. SELECT * FROM `things` where md5(concat(id,'some salt')) = md5('1some salt'); Is there a standard practice for obscuring IDs in this kind of situation?

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  • Symfony models with foreign keys

    - by Daniel Hertz
    So I have 2 models. Users and Groups. Each group has a user as the creator and a group has many users. The FK of these tables are set up correctly, but I was wondering if there was an easier way to get all related FK objects from other objects. For example, with a group object, is there a built in method to get the user object of the creator? Or for a user, is there a built in method to get all group object that he belongs to? I couldn't find out how to do this with the documentation on the symfony page. From what I see I feel like I need to create methods and use doctrine to access the appropriate tables using the current objects id and so on. Thanks!

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