Understanding the Concept of Cryptography in SQL Server

Cryptography in SQL Server is the advance technique of encrypting and decrypting the data existing in SQL Server databases for preventing unauthorized access. This technique is important to protect databases from illegal activities as it helps in authentication, authorization, assigning permissions and encryption/decryption operations. There are various functions that can be used for ciphering the data components in SQL databases, and these includes.

i.      Symmetric Keys
ii.    Asymmetric Keys
iii.   One-Way Hashing

In the upcoming section, detailed description about all these terms has been provided.

Symmetric Keys:

Under this approach, a single key is used to encrypt or decrypt the data. The key that is used to encrypt data will exactly be used to decrypt that data. The key is created at initial stage when SQL Server is started; and is utilized for protecting sensitive data.

There are several pros and cons associated to the Symmetric Key and these parameters include:

·    Quickly executable with simple encryption algorithms and faster performance.
·     Random codes easily remembered by users and offers maximum security.

·     The major drawback of the Symmetric keys is their ’Symmetry’ itself.
·      An easily predictable password makes it the point for email ‘phishing’.

Asymmetric Keys:

‘Asymmetric Keys’ exist in the pair of keys; one private and another public. Data when encrypted via one key will only be decrypted through the alternate key. Here, users with access to public key can encrypt the data components; but the encrypted data can only be de-ciphered by the one with access to the private key.

Likewise Symmetric keys, this approach is also associated with corresponding pros and cons:
· Capable of handling issues associated to identity with appropriate verification algorithms.
·    Ensures complete security to the users and the database elements.
·    Complex keys those are difficult to remember with comparatively slower performance.
·     IT requires implementing more computing resources for using the key.

One-Way Hash:

The numbers generated corresponding to the components of a message or document is known as ‘hash’.  Hash value is affected by the addition or deletion of text and even with the case of the alphabets. Different values are generated for uppercase alphabets but when the letters are changed to lowercase; the corresponding value gets modified instantly. Hash algorithm is associated with some distinct properties that are defined in this section.

i.   Even a minute modification in the document text will lead to generation of entirely different hash codes.
ii.  If changes are made in the document; it is harder to detect the modifications via examining the hash values. Due to this feature; this is known as “One Way Hash”.
iii.   It is often considered an efficient approach as these files are very large in volume and thus difficult to navigate.
The advantages and disadvantages relevant to this approach are as under:
·    This approach is highly efficient and faster.
·     Ensures improved data security as the hash codes are difficult to understand.
·    Two different messages can generate similar hash values.
·     Individual with sound knowledge could detect and break the hash values.

Public Key Infrastructure:

The public key infrastructure can better be understood by use of an example: Suppose, the activities performed by a team are under analysis. A member outside the team sends an encrypted message to the monitored team. To gain access to the message, you can capture the public key through DNS hack and can assign any public key according to you. Further, you can capture the messages sent to the monitored team from outside resources and can decrypt the message by using the private key. You can even re-encrypt the text to prevent detection of the original information and can transfer it to the team. This activity is often known as “man-in-the-middle” attack.

Certificate Authorities:

You can protect yourself from “man-in-the-middle” attacks and any fraudulent activities through setting a confirmable association between individual identity and the personal key. Here, digital signatures work as a ‘Notary Public’ that ensures that the information mentioned herein is true and hence verified. The highest authority in the certification hierarchy is known as “root authority”.

SQL Server Authentication Cryptography:

SQL Server security parameters comprises of two parts:

i.       Authentication: To verify the identity of a user.
ii.     Authorization: Rights and Permissions assigned to a user.

Authentication refers to the procedure of authenticating or verifying the user’s identity and is further categorized into two sections. These segments include “Windows Authentication” and “SQL Server Authentication”.

Authorization is the process of granting or assigning permissions and appropriate rights to the users existing in the database. The user can then act according to the assigned authorities on the incorporated data components and database files.


The techniques of Cryptography in SQL Server are categorized into distinct segments and these can be used as per requirement by the DBA or the users. These techniques and measures ensure that the incorporated data is secured and is protected from various sorts of external threats. Sound understanding and technical expertise is required to implement these measures; to ensure security and integrity of data.

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