Dbm Power

How to convert photon density (unit: /cm3) to optical power (unit: dBM)?

You need to know the frequency of the photon ν. The energy of each photon is E = h*ν. The energy density is photon density ρ*h*ν J/cm³. If the beam has uniform density and collimated, the power across any surface of area A is W = ρ*h*ν*c*A Watt

The optical power is

P(dBm) = 10*log(ρ*h*ν*c*A) + 30

dBm means it is referenced to 1 mW

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This article is dedicated to the analysis of mandatory access restriction for Oracle DBMS. As a result, several leakage channels discovered.

For information many DBMS-based system is often a problem to implement access restriction, which is valuable information into account. Usually crucial information systems for large-scale government or business (use of geographic information systems is, or document management systems). This system usually involves mandatory access model. One of the features of the model is required to prevent any accidental or intentional impairment of value information by controlling information flow. Mandatory access model is implemented by labeling all the subjects and objects belonging to the restraint system access.

Oracle DBMS is currently one of the most powerful and popular industrial DBMS. From the component Oracle9i version of Oracle Label Security (OLS) is carried out, which makes possible the organization of compulsory access to stored data. OLS is a set of procedures and limitations built into the core database, allowing the implementation of access control register. To ensure that MCO is required to create a security policy that contains a set of labels. Whenever this policy is created to be applied to tables protected and users should receive the rights of labels.
Analysis for channels of information leakage sounds good for the confidential review system.
We are offering the following algorithm for joint analysis of mandatory access model.
1) the types of Access objects are determined according to the published documentation and investigation of the DBMS (eg, tables, strings, or columns).
2) SQL commands are discussed in terms of how users can modify the access objects.
3) Several objects with different levels of confidentiality are created for each access object type.
4) Various user (subject access) accounts are created with different access rights required.
5) A series of SQL queries is formed, which are run with different mandatory access restriction of the rights and objects with a different level of confidentiality. According to the analysis of performance of these consultations is possible to construct a model of access, and make a determination whether the system has vulnerabilities that can lead to leakage or corruption of information confidential.
Let us consider the access objects of OLS. These are the records of the table, which have unique labels. It is often implied that tables are objects access to OLS, because the security policy applies to tables. However, the tables do not have labels, but only contain the tag ranks.
The following basic operations of SQL to handle individual records:
– Create – creating a new record;
– SELECT – reading an existing record;
– UPDATE – Modification of an existing record;
– DELETE – deletion of a record.
Our experiments consisted of sequences of consultations convened by users of different access rights to objects of different levels of confidentiality. These experiments have allowed the construction of the model of mandatory access to the records of the Operation. We define two variables: I and J. I is an object tag value. Lower values indicate the highest level of confidentiality (the value of 0 corresponds to "top secret "). J is a value of subject access level.
The model can be presented in formal terms as follows:

1. CREATE \ SELECT \ Update \ DELETE, j = i
2. SELECT, ji

Such a model of mandatory access logging level is quite correct and meets the criteria of Bell-La Padula security model. Thus MCO functioning properly at the level of the table records.
However, next to the records as representing the stored data, users can interact with other data representation, which is not affected by the mandatory access policy. The tables are an example of such objects. Users themselves can modify the structure of tables, ie, add new fields, change their names, and modify data types. OLS loses its ability to function properly in the table level.
For example, a user with the highest binding rights has the right to create a new field in a table. The field name itself may be confidential, and the mechanism of MCO does not prevent such operation. A user with lower access rights is always a possibility of consultation with the names of all fields.
For example, a new field is created with the name of new_password_xxx (where xxx is a top-secret information) with the following SQL query:
Add ALTER TABLE user1.test_table (new_password VARCHAR2 (30));
If another user that has no statutory right to run the following query (SELECT * FROM user1.test_table;), one obtains a set of empty data, however all ofuser1.test_table field names are exposed. As demonstrated above, the name of the column may contain classified information.
Of operations shown in the example of creating duplex channels of data exchange among individuals with access rights above and below, and thus can cause information leakage classified information.
On the subject of the above, the mandatory access model implemented in Oracle is not complete, and this fact makes possible the exchange of classified information, without any access control system required, which decreases the value of information.
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