[CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts

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[CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts

Amlan Deb
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 

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Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts

clementdupuis
Administrator
Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:


Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: [hidden email]

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <[hidden email]> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 


_______________________________________________
You can find the list archive at:
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_______________________________________________
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CISSPstudy mailing list
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[CCCure CISSP] Doubt regarding Rijndael algorith

Amlan Deb
 
Thanks Clement for the clarification regarding AES :).
 
However, I would like to ask the same questions with regard to the Rijndael algorithm now (independent of how it is implemented in AES) based on the facts below:
 
Key sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
Block sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
 
 
My doubt: While using the original Rijndael algorith (independent of how it is implemented in AES):
 
can the Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same all the time (i.e. both the key and block size are 128/160/192/224/256 bits) ?
 
Thanks,
Amlan

--- On Mon, 6/3/13, Clement Dupuis <[hidden email]> wrote:

From: Clement Dupuis <[hidden email]>
Subject: Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts
To: "The CISSP Study Mailing list" <[hidden email]>
Date: Monday, June 3, 2013, 2:21 AM

Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: clement@...

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <amlan_deb999@...> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 

_______________________________________________
You can find the list archive at:
http://cissp-study.3965.n7.nabble.com/

CISSPstudy mailing list
CISSPstudy@...

To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
http://cccure.org/mailman/listinfo/cisspstudy_cccure.org



-----Inline Attachment Follows-----

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CISSPstudy@...

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Re: [CCCure CISSP] Doubt regarding Rijndael algorith

Amlan Deb
 
Also, a related question - if the Qs. in the exam is asking regarding Rijndael algorithm, we should answer only from the point of view of the original implementation of Rijndael itself right (and not it's AES implementation)?
 
Thanks,
Amlan

--- On Fri, 6/7/13, Amlan Deb <[hidden email]> wrote:

From: Amlan Deb <[hidden email]>
Subject: Doubt regarding Rijndael algorith
To: "The CISSP Study Mailing list" <[hidden email]>
Date: Friday, June 7, 2013, 1:51 PM

 
Thanks Clement for the clarification regarding AES :).
 
However, I would like to ask the same questions with regard to the Rijndael algorithm now (independent of how it is implemented in AES) based on the facts below:
 
Key sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
Block sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
 
 
My doubt: While using the original Rijndael algorith (independent of how it is implemented in AES):
 
can the Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same all the time (i.e. both the key and block size are 128/160/192/224/256 bits) ?
 
Thanks,
Amlan

--- On Mon, 6/3/13, Clement Dupuis <[hidden email]> wrote:

From: Clement Dupuis <[hidden email]>
Subject: Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts
To: "The CISSP Study Mailing list" <[hidden email]>
Date: Monday, June 3, 2013, 2:21 AM

Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: clement@...

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <amlan_deb999@...> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 

_______________________________________________
You can find the list archive at:
http://cissp-study.3965.n7.nabble.com/

CISSPstudy mailing list
CISSPstudy@...

To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
http://cccure.org/mailman/listinfo/cisspstudy_cccure.org



-----Inline Attachment Follows-----

_______________________________________________
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CISSPstudy mailing list
CISSPstudy@...

To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
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_______________________________________________
You can find the list archive at:
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CISSPstudy mailing list
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To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
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Re: [CCCure CISSP] Doubt regarding Rijndael algorith

clementdupuis
Administrator
In reply to this post by Amlan Deb
Good day Amlan,

Your question is timely.  I had the same question in class yesterday and took some time to update one of the quiz question last night.

See below

Take care

Clement

The correct answer is:  Maximum key size is 512 bits

The above statement is NOT true and thus the correct answer.   The maximum key size on Rijndael is 256 bits.

There are some differences between Rijndael and the official FIPS-197 specification for AES.

Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits.  Namely, Rijndael allows for both key and block sizes to be chosen independently from the set of { 128, 160, 192, 224,  256 } bits.  (And the key size does not in fact have to match the block size). 

However, FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

  Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128


So in short:

Rijndael and AES differ only in the range of supported values for the block length and cipher key length.

For Rijndael, the block length and the key length can be independently specified to any multiple of 32 bits, with a minimum of 128 bits, and a maximum of 256 bits.

AES fixes the block length to 128 bits, and supports key lengths of 128, 192 or 256 bits only. 

 

References used for this question:

http://blogs.msdn.com/b/shawnfa/archive/2006/10/09/the-differences-between-rijndael-and-aes.aspx

and

http://csrc.nist.gov/CryptoToolkit/aes/rijndael/Rijndael.pdf



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: [hidden email]

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Fri, Jun 7, 2013 at 4:21 AM, Amlan Deb <[hidden email]> wrote:
 
Thanks Clement for the clarification regarding AES :).
 
However, I would like to ask the same questions with regard to the Rijndael algorithm now (independent of how it is implemented in AES) based on the facts below:
 
Key sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
Block sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
 
 
My doubt: While using the original Rijndael algorith (independent of how it is implemented in AES):
 
can the Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same all the time (i.e. both the key and block size are 128/160/192/224/256 bits) ?
 
Thanks,
Amlan

--- On Mon, 6/3/13, Clement Dupuis <[hidden email]> wrote:

From: Clement Dupuis <[hidden email]>
Subject: Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts
To: "The CISSP Study Mailing list" <[hidden email]>
Date: Monday, June 3, 2013, 2:21 AM

Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +<a href="tel:703%20535%208600" value="+17035358600" target="_blank">703 535 8600
Mobile: <a href="tel:%2B1%20407%20433%206444" value="+14074336444" target="_blank">+1 407 433 6444

Email: clement@...

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <amlan_deb999@...> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 


_______________________________________________
You can find the list archive at:
http://cissp-study.3965.n7.nabble.com/

CISSPstudy mailing list
CISSPstudy@...

To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
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-----Inline Attachment Follows-----

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CISSPstudy@...

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_______________________________________________
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CISSPstudy mailing list
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To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
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_______________________________________________
You can find the list archive at:
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CISSPstudy mailing list
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To UNSUBSCRIBE, SUBSCRIBE, or MANAGE your accout visit the link below:
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CCCure Founder and Owner
CLO @ SecureNinja.Com
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Re: [CCCure CISSP] Doubt regarding Rijndael algorith

Amlan Deb
 
Thanks Clement.
 
So if the Qs. mentions "Advanced Ecryption Standard (Rijndael)" - we should answer from the point of view of AES.
 
if the Qs. mentions "Rijndael: - we should answer from the point of view of the original Rijndael algorithm.
 
Is my understanding correct?
 
Thanks,
Amlan


--- On Fri, 6/7/13, Clement Dupuis <[hidden email]> wrote:

From: Clement Dupuis <[hidden email]>
Subject: Re: [CCCure CISSP] Doubt regarding Rijndael algorith
To: "The CISSP Study Mailing list" <[hidden email]>
Date: Friday, June 7, 2013, 2:49 PM

Good day Amlan,

Your question is timely.  I had the same question in class yesterday and took some time to update one of the quiz question last night.

See below

Take care

Clement

The correct answer is:  Maximum key size is 512 bits
The above statement is NOT true and thus the correct answer.   The maximum key size on Rijndael is 256 bits.
There are some differences between Rijndael and the official FIPS-197 specification for AES.
Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits.  Namely, Rijndael allows for both key and block sizes to be chosen independently from the set of { 128, 160, 192, 224,  256 } bits.  (And the key size does not in fact have to match the block size). 
However, FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:
  Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

So in short:
Rijndael and AES differ only in the range of supported values for the block length and cipher key length.

For Rijndael, the block length and the key length can be independently specified to any multiple of 32 bits, with a minimum of 128 bits, and a maximum of 256 bits.

AES fixes the block length to 128 bits, and supports key lengths of 128, 192 or 256 bits only. 
 
References used for this question:
and


Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: clement@...

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

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On Fri, Jun 7, 2013 at 4:21 AM, Amlan Deb <amlan_deb999@...> wrote:
 
Thanks Clement for the clarification regarding AES :).
 
However, I would like to ask the same questions with regard to the Rijndael algorithm now (independent of how it is implemented in AES) based on the facts below:
 
Key sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
Block sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
 
 
My doubt: While using the original Rijndael algorith (independent of how it is implemented in AES):
 
can the Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same all the time (i.e. both the key and block size are 128/160/192/224/256 bits) ?
 
Thanks,
Amlan

--- On Mon, 6/3/13, Clement Dupuis <clement.dupuis@...> wrote:

From: Clement Dupuis <clement.dupuis@...>
Subject: Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts
To: "The CISSP Study Mailing list" <cisspstudy@...>
Date: Monday, June 3, 2013, 2:21 AM

Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

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GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

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-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <amlan_deb999@...> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 

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Re: [CCCure CISSP] Doubt regarding Rijndael algorith

clementdupuis
Administrator
That is correct,

There are two different beasts.

One was used to build the others but the AES standard has it's own set of key sizes and blocks.

The reason they pick those sizes were related to avoiding some of the potentials attacks.

Best regards

Clement


Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

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On Fri, Jun 7, 2013 at 5:54 AM, Amlan Deb <[hidden email]> wrote:
 
Thanks Clement.
 
So if the Qs. mentions "Advanced Ecryption Standard (Rijndael)" - we should answer from the point of view of AES.
 
if the Qs. mentions "Rijndael: - we should answer from the point of view of the original Rijndael algorithm.
 
Is my understanding correct?
 
Thanks,
Amlan


--- On Fri, 6/7/13, Clement Dupuis <[hidden email]> wrote:

From: Clement Dupuis <[hidden email]>
Subject: Re: [CCCure CISSP] Doubt regarding Rijndael algorith

To: "The CISSP Study Mailing list" <[hidden email]>
Date: Friday, June 7, 2013, 2:49 PM


Good day Amlan,

Your question is timely.  I had the same question in class yesterday and took some time to update one of the quiz question last night.

See below

Take care

Clement

The correct answer is:  Maximum key size is 512 bits
The above statement is NOT true and thus the correct answer.   The maximum key size on Rijndael is 256 bits.
There are some differences between Rijndael and the official FIPS-197 specification for AES.
Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits.  Namely, Rijndael allows for both key and block sizes to be chosen independently from the set of { 128, 160, 192, 224,  256 } bits.  (And the key size does not in fact have to match the block size). 
However, FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:
  Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

So in short:
Rijndael and AES differ only in the range of supported values for the block length and cipher key length.

For Rijndael, the block length and the key length can be independently specified to any multiple of 32 bits, with a minimum of 128 bits, and a maximum of 256 bits.

AES fixes the block length to 128 bits, and supports key lengths of 128, 192 or 256 bits only. 
 
References used for this question:
and


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Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
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The CCCure Family of Portals
----------------------------------------------------------------------------------------------
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The CCCure Quiz Engine
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The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
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Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Fri, Jun 7, 2013 at 4:21 AM, Amlan Deb <amlan_deb999@...> wrote:
 
Thanks Clement for the clarification regarding AES :).
 
However, I would like to ask the same questions with regard to the Rijndael algorithm now (independent of how it is implemented in AES) based on the facts below:
 
Key sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
Block sizes of 128, 160, 192, 224, and 256 bits are supported by the Rijndael algorithm
 
 
My doubt: While using the original Rijndael algorith (independent of how it is implemented in AES):
 
can the Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same all the time (i.e. both the key and block size are 128/160/192/224/256 bits) ?
 
Thanks,
Amlan

--- On Mon, 6/3/13, Clement Dupuis <clement.dupuis@...> wrote:

From: Clement Dupuis <clement.dupuis@...>
Subject: Re: [CCCure CISSP] Qs10 Cryptography: cccure QuizEngn doubts
To: "The CISSP Study Mailing list" <cisspstudy@...>
Date: Monday, June 3, 2013, 2:21 AM

Good day Amlan,

Your view of DES below is accurate.

As far as AES then it is not accurate:

Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

AES is the advanced encryption standard defined by FIPS 197.    It is implemented differently than Rijndael:

FIPS-197 specifies that the block size must always be 128 bits in AES, and that the key size may be either 128, 192, or 256 bits.  Therefore AES-128, AES-192, and AES-256 are actually:

Key Size (bits) Block Size (bits)
AES-128 128 128
AES-192 192 128
AES-256 256 128

See FIPS 197 for more details.

Take care

Clement



Clement Dupuis, CD

Chief Learning Officer (CLO) and Security Evangelist
GCFW, GCIA, Security+ 301, CEH V7, CCSA, CCSE,  + 12 others

SecureNinja
Office : +703 535 8600
Mobile: +1 407 433 6444

Email: clement@...

Web: www.secureninja.com

Connect with me on LinkedIn | Follow me on Twitter


Description: Secure Ninja @ LinkedinDescription: See Us @ YoutubeDescription: Like us on FacebookDescription: Fallow us Twitter

901 N. Pitt Street, Suite 105
Alexandria, VA  22314

Description: Description: sn_logo

In Cyberspace:

[hidden email]
Clement Dupuis, CD
President/Founder/Chief Security Evangelist
The CCCure Family of Portals
----------------------------------------------------------------------------------------------
Maintainer of :

The CCCure Quiz Engine
https://www.freepracticetests.org/quiz/index.php?page=home

The CCCure Family of Portals
http://www.cccure.org

The Professional Security Testers Warehouse
http://www.professionalsecuritytesters.org/

Knowledge sharing and giving back to the community

-------------------------------------------------------------------------------------------------------
>>  Call me to get the best CISSP, Security+, or other Security related training  <<
-------------------------------------------------------------------------------------------------------


On Sun, Jun 2, 2013 at 4:30 PM, Amlan Deb <amlan_deb999@...> wrote:
 
Hello everyone,
 
I have some doubts regarding some cccure Quiz questions and concepts mentioned below. Would really appreciate it if you could take out some time and help me with them. Request you to please provide a quick reply as I need to appear for the exam in the month of July.
 
Thanks,
Amlan
 

 

Some other doubts
========

 

Is my understanding correct that:

1. if the Qs asks “the Key length of DES” – the answer is 64 bits

2. if the Qs asks “the true Key length of DES” – the answer is 56 bits

3. if the Qs asks “the effective Key length of DES” – the answer is 56 bits

 

4. Can the AES Key size and Block size be different from each other (i.e. key size = 128 bits and Block size = 192 bits or vice-versa or any other unequal combination) or do they have to be same (i.e. both the key and block size are 128 bits/192 bits/256 bits)

 


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