S-Box creation in the Advanced Encrypted Standard(AES)!!!

Hello Every1

I am currently working on AES. i have a doubt about S-Box and Inverse S-box in the AES. i want to know is we have to create a different S-box for different key or the same S- box is used for all the keys!!!


Thanks and Regards

Mukesh Goyal

S-Box is same ,it doesn't depend on any particular choice of Key

blooz is right. One sbox and one invert sbox are needed.

see

https://opencores.org/websvn,filede...e&path=/aes_core/trunk/rtl/verilog/aes_sbox.v

https://opencores.org/websvn,filede...th=/aes_core/trunk/rtl/verilog/aes_inv_sbox.v

thanks for ur reply bt i study that s-box is generated by two operation :1) multiplicative inverse of matrix element and then 2) affine transformation
if we will try to calculate s-box for each key seperately then it provide better security. Same we can do with inverse s-box..
Am i correct?

AES S-box was specifically designed to be resistant to linear and differential cryptanalysis. This was done by minimizing the correlation between linear transformations of input/output bits, and at the same time minimizing the difference propagation probability.

Don't link key and S-Box ....

S-Box is same for every Key

If you want to generate some other S-box then it will mean that you are going for some other Encryption Algorithm .In otherwords the S-box is fixed for AES


AES is a Standard and the s-box must be same ,else it won't be AES

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Mukesh10 said:

thanks for ur reply bt i study that s-box is generated by two operation :1) multiplicative inverse of matrix element and then 2) affine transformation
if we will try to calculate s-box for each key seperately then it provide better security. Same we can do with inverse s-box..
Am i correct?

Click to expand...

If you are trying to develop an IP Core or Software implementation it's better you follow the FIPS Standard otherwise if you are researcher going to experiment with the AES variants ,to produce AES variants then it's possible

This is is something you can refer
Key-Dependent S-Box Generation in AES Block
Cipher System

http://www.mii.lt/informatica/pdf/INFO743.pdf

Thanks Blooz

I got ir wat u r trying to convey!!! now can u tell me one more thing in MIxcolumn operation : for 128 bit key the mulptiple matrix is :

2 3 1 1
1 2 3 1
1 1 2 3
3 1 1 2


then wat is the multiple matrix for 192 bit key and for 256 bit key.

Mukesh10 said:

Thanks Blooz

I got ir wat u r trying to convey!!! now can u tell me one more thing in MIxcolumn operation : for 128 bit key the mulptiple matrix is :

2 3 1 1
1 2 3 1
1 1 2 3
3 1 1 2


then wat is the multiple matrix for 192 bit key and for 256 bit key.

Click to expand...

Yes it is same

Here is the Original Rijndael
h**p://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf

@Blooz
Sir i am working in AES algorithm project.i have one doubt that how can we implement combinational circuit instead of lookup table and how a key expansion is going to done,whether we have given an input key for key expansion??


Tom mathew

jasonbourne1988 said:

@Blooz
Sir i am working in AES algorithm project.i have one doubt that how can we implement combinational circuit instead of lookup table and how a key expansion is going to done,whether we have given an input key for key expansion??


Tom mathew

Click to expand...

@jason its very simple method to implement AES through combination circuit . you have to search on Google for combination circuit or hardware implementation of AES. each operation is implemented separately by combinational circuit like s-box , mixcolumn, shiftrow and all .