3C13/D6
II. Selected Database Issues
Part 1: Security
Lecture 2
Lecturer: Chris Clack
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1. Content
Content
2.0 Objectives
2.1 Countermeasures: computer-based controls (BRAVE)
- 2.1.1 Encryption
2.2 Authentication and Authorisation in Microsoft Access DBMS
- 2.2.1 Authentication: Setting a password
- 2.2.2 Authorisation: User-level security
2.3 Authorisation in Oracle DBMS
- 2.3.1 Privileges
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2.0 Objectives
Objectives
In this Lecture you will learn:
1.
The final element of “BRAVE” security control mechanisms:
–
Encryption
2.
Microsoft Access authentication and authorisation measures
3.
Oracle DBMS security measures
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2.1 BRAVE: Encryption
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2.1 Countermeasures: computer-based controls
Encryption
• Encryption: the encoding of the data by a special algorithm
that renders the data unreadable by any program without the
decryption key.
• Encode data of a sensitive nature as a precaution against
possible external threats.
The DBMS can access the data after decoding it, although there is a
degradation in performance as it takes time to decode.
• Encryption protects data transmitted over communication lines.
There are a number of techniques for encoding data…
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2.1 Countermeasures: computer-based controls
Encryption
• Irreversible encryption
– Does not permit the original data to be known.
– However, the encrypted data can be used to obtain valid statistical
information.
• Reversible encryption
– More common.
– To transmit data securely over an insecure network requires the
use of a cryptosystem.
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2.1 Countermeasures: computer-based controls
Encryption
•
Cryptosystem Includes:
– Encryption key to encrypt the data (plaintext).
– Encryption algorithm that, with the encryption key, transforms the
plaintext into ciphertext
– Decryption key to decrypt the ciphertext
– Decryption algorithm that, with the decryption key, transforms the ciphertext
back into plaintext.
text
encryption algorithm
encryption key
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cypher
text
decryption algorithm
text
decryption key
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2.1 Countermeasures: computer-based controls
Encryption
• Symmetric Encryption:
– Uses the same key for encryption and decryption.
– Requires a secure communication line for exchanging the key. Most users
don't have a secure line.
– To be really secure the key should be as long as the message, most
however use shorter keys.
• Asymmetric Encryption:
– Uses different keys.
Symmetric Example: DES (Data Encryption Standard)
– Developed by IBM.
– Not universally regarded as being secure. Some authors say a larger key
is required.
– PGP Pretty Good Privacy uses a 128-bit symmetric algorithm for bulk
encryption of the data it sends.
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2.1 Countermeasures: computer-based controls
Encryption
• Keys with 64-bits are now considered breakable by major
governments, though at substantial cost.
• This technology will be within the reach of organized criminals, major
organizations and smaller governments either already or very soon
• It is probable that keys with 128-bits will remain unbreakable for
the foreseeable future.
• The terms strong authentication and weak authentication are
sometimes used to distinguish between algorithms that cannot be
broken with existing technologies and knowledge (strong) and those
that can (weak).
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2.1 Countermeasures: computer-based controls
Encryption
Asymmetric Example: Public key systems. Two keys are used. One is
public and one is private. The encryption algorithm may also be
public. Anyone can send an encoded message using the public key
and algorithm given by the owner. But only the owner of the private
key may decipher the message.
•
A digital signature can also be used to prove the message came from the
person who claimed to have sent it (see later lecture).
•
RSA is the most well known asymmetric encryption (the name derives from
the initials of the algorithm designers).
•
Generally, asymmetric algorithms are much slower to execute. In practice the
two types of encryption are used together.
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2.2 Authentication and authorisation in
Microsoft Access DBMS
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2.2 Authentication & authorisation in Microsoft Access DBMS
Authentication and authorisation in
Microsoft Access DBMS
Prerequisite course covered Microsoft Access 2000
DBMS and SQL GRANT and REVOKE statements
Access instead of GRANT and REVOKE statements, Access
provides:
• system security : setting a password for opening a database (authentication)
• data security : user-level security, which limits the parts of the database a user
can read or update (authorisation)
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2.2 Authentication & authorisation in Microsoft Access DBMS
Authentication in Microsoft Access DBMS
Example (Password):
Password set from Tools,
Security menu
Secure.
Access
encrypts
password
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2.2 Authentication & authorisation in Microsoft Access DBMS
Authorisation in Microsoft Access DBMS
Example (user-level security)
Within the Microsoft
Access workgroup
information File users
are identified as
belonging to a group.
Default groups:
- administrator
(Admin group)
- users (Users
group).
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2.2 Authentication & authorisation in Microsoft Access DBMS
Authorisation in Microsoft Access DBMS
Example (user-level security: Permissions)
• Permissions granted to groups and
users
• Dialog box used to regulate how
they can work with given objects
• No. of possible permissions:
Open/Run, Read Design, Modify
Design, Update Data, Read Data,
Delete Data etc...
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2.3 Authorisation in Oracle DBMS
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2.3 Authorisation in Oracle DBMS
Authorisation in Oracle DBMS
Privileges
Privilege: the right to execute a particular type of SQL
statement or to access another user’s objects.
Some examples of Oracle privileges are:
•connect to the database (create a session)
•create a table
•select rows from another user’s table
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2.3 Authorisation in Oracle DBMS
Authorisation in Oracle DBMS
Privileges
There are two distinct categories of privileges in Oracle:
1. System privileges: the right to perform a particular action, or to perform an
action on schema objects of a certain type. Control privileges associated with
some schema objects (clusters, indexes and triggers).
Example: creation of table spaces or of users in a database.
Privileges granted or revoked in two ways:
1. Grant System Privileges/Roles dialog box and Revoke System
Privileges/Roles dialog box of Oracle Security Manager.
2. SQL GRANT and REVOKE statements.
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2.3 Authorisation in Oracle DBMS
Authorisation in Oracle DBMS
Privileges
2. Object privileges: the right to perform a particular action on a specific table,
view, sequence, procedure, function or package.
Example: the privilege to delete rows from the Staff table.
A user automatically has all object privileges for schema objects contained in
their schema.
They can grant object privileges on any schema object owned.
The inclusion in the grant of the WITH GRANT OPTION (of the GRANT
statement) allows the user to further grant the object privileges to other users.
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2.3 Authorisation in Oracle DBMS
Authorisation in Oracle DBMS
Privileges
A user can receive a privilege in two different ways:
1. Privileges can be granted to users explicitly.
Example: GRANT INSERT ON PropertyForRent TO
Beech, means the object privilege “insert rows” has
been granted to Mr Beech on the said table.
2. Privileges can be granted to a role.
The role can then be granted to one or more
users.
Example: the object privileges insert, delete
and update could be granted to the role
`Assistant’ User Beech can then be granted the
role Assistant.
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`Role ’ : a named
group of privileges
A user can access
several roles and
several users can be
assigned the same
role.
This is a better and
easier way to
manage privileges.
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2.4 Summary
Summary
1.3 The final “BRAVE” countermeasure

E ncryption
2.2 Authentication and authorisation in Microsoft
Access DBMS


NEXT LECTURE:
DBMS and Web Security
- Firewalls
- Signatures
- Certificates
Setting a password
User-level security
2.3 Authorisation in Oracle DBMS

Privileges
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