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How to compute values using ' log' and 'sqrt' on javacard ?

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btwtiger
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How to compute values using ' log' and 'sqrt' on javacard ?

Post by btwtiger » Wed Jun 10, 2015 7:30 am

Recently,I need to compute values using log and sqrt on a JavaCard. Is there any class for javacard to solve this issue ?
Many thanks.
Last edited by btwtiger on Wed Jun 10, 2015 10:31 pm, edited 4 times in total.
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horse dream
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Re: How to compute values using ' log'?

Post by horse dream » Wed Jun 10, 2015 7:43 am

Javacard doesn't support Math class and also only supports boolean, byte, short, and optionally int. Maybe you can create your own class with tricky ways and of course the result is not precise. If you let server/terminal side do complex calculation/encryption, the card only stores data,maybe you can get it working.
Last edited by horse dream on Wed Jun 10, 2015 9:51 pm, edited 1 time in total.

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btwtiger
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Re: How to compute values using ' log'?

Post by btwtiger » Wed Jun 10, 2015 9:46 pm

horse dream wrote:Javacard doesn't support Math class and also only supports boolean, byte, short, and optionally int. Maybe you can create your own class with tricky ways and of course the result is not precise. If you let server/terminal side do complex calculation/encryption, the card only stores data,maybe you can get it working.


Sorry to tell you I have to do all the calculation on the card side. Anyhow,thank you for your attention.
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Larson
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Re: How to compute values using ' log' on javacard ?

Post by Larson » Wed Jun 10, 2015 10:04 pm

I've not came across such a class yet. The only way to meet your request is to use some limited tricks with the crypto API.

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btwtiger
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Re: How to compute values using ' log' on javacard ?

Post by btwtiger » Wed Jun 10, 2015 10:13 pm

Larson wrote:I've not came across such a class yet. The only way to meet your request is to use some limited tricks with the crypto API.


Would you please give me a example ?
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Larson
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Re: How to compute values using ' log' on javacard ?

Post by Larson » Wed Jun 10, 2015 10:28 pm

e.g. You can perform an RSA modulo exponentiation using 2 as public key and a large modulus to perform squares.

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