Our Online Store have the new products: RFID antenna board. Currently it can work with JC10M24R and JCOP4 card chips.
Compared with normal cards, the antenna board module has a smaller size and fixed holes, which is easy to integrate in the IOT(Internet Of Things) project.

Multiply big numbers

JavaCard Applet Development Related Questions and Answers.
djordjem
Posts: 5
Joined: Fri Dec 22, 2017 5:59 am
Points :442
Contact:

Multiply big numbers

Post by djordjem » Tue Apr 17, 2018 11:27 am

Hello everyone

Does anyone know how I can multiply two big numbers on javacard? I have two byte arrays size of 128 bytes.
I was trying to implement code in link below but it doesn't work for me.
https://stackoverflow.com/questions/36966764/using-rsa-for-modulo-multiplication-leads-to-error-on-java-card

Best regards,
djordjem

User avatar
Tolice
Posts: 40
Joined: Wed May 20, 2015 2:41 am
Points :254
Contact:

Re: Multiply big numbers

Post by Tolice » Tue Apr 17, 2018 10:07 pm

You can specifically describe the problem in here, so that others can help you better

roundtable
Posts: 18
Joined: Mon Sep 18, 2017 9:52 pm
Points :240
Contact:

Re: Multiply big numbers

Post by roundtable » Wed Apr 18, 2018 5:00 am

HI, guy, are you sure your javacard provide those special API for big integer modular arithmetic ? the standard javacard API can't support your requirements. you may need special javacard equipped with non-standard API to support big integer operation, such as modular add/sub/multiply/GCD and so on. you can contact to javacardos@gmail.com for details.

Riddle
Posts: 12
Joined: Mon Dec 28, 2015 11:41 pm
Points :70
Contact:

Re: Multiply big numbers

Post by Riddle » Wed Apr 18, 2018 5:39 am

What format do you used? decimal or hexadecimal? The big number is modular multiplication algorithm, the decimal and hexadecimal are not the same, but the hexadecimal is easier.

BirdKing
Posts: 86
Joined: Wed Nov 04, 2015 7:23 am
Points :656
Contact:

Re: Multiply big numbers

Post by BirdKing » Wed Apr 18, 2018 5:57 am

It's like private APIs defined by the company. Is big-end or little-end ?

djordjem
Posts: 5
Joined: Fri Dec 22, 2017 5:59 am
Points :442
Contact:

Re: Multiply big numbers

Post by djordjem » Wed Apr 18, 2018 8:06 am

Riddle wrote:What format do you used? decimal or hexadecimal? The big number is modular multiplication algorithm, the decimal and hexadecimal are not the same, but the hexadecimal is easier.

I'm using hexadecimal format.

BirdKing wrote:It's like private APIs defined by the company. Is big-end or little-end ?

It's big-end.

Code: Select all

x = {(byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42, (byte) 0xD0, (byte) 0x84, (byte) 0xA1, (byte) 0x9E, (byte) 0xCF, (byte) 0x56, (byte) 0x1B, (byte) 0xBD, (byte) 0x7E, (byte) 0x06, (byte) 0xF6, (byte) 0x4A, (byte) 0x47, (byte) 0xB7, (byte) 0x60, (byte) 0x8B, (byte) 0x3E, (byte) 0x42};

y = {(byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C, (byte) 0x06, (byte) 0x03, (byte) 0x55, (byte) 0x1D, (byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C, (byte) 0x06, (byte) 0x03, (byte) 0x55, (byte) 0x1D, (byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C, (byte) 0x06, (byte) 0x03, (byte) 0x55, (byte) 0x1D, (byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C, (byte) 0x06, (byte) 0x03, (byte) 0x55, (byte) 0x1D, (byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C, (byte) 0x06, (byte) 0x03, (byte) 0x55, (byte) 0x1D, (byte) 0x3D, (byte) 0x21, (byte) 0x22, (byte) 0x9F, (byte) 0x05, (byte) 0x63, (byte) 0x03, (byte) 0xF2, (byte) 0xF9, (byte) 0x87, (byte) 0x7E, (byte) 0x9A, (byte) 0x3E, (byte) 0x7D, (byte) 0x40, (byte) 0xE1, (byte) 0x30, (byte) 0x0C};

p = 0x00b10b8f96a080e01dde92de5eae5d54ec52c99fbcfb06a3c69a6a9dca52d23b616073e28675a23d189838ef1e2ee652c013ecb4aea906112324975c3cd49b83bfaccbdd7d90c4bd7098488e9c219a73724effd6fae5644738faa31a4ff55bccc0a151af5f0dc8b4bd45bf37df365c1a65e68cfda76d4da708df1fb2bc2e4a4371


x*y = 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

x*y mod p = 0x869ad6700a26f16d80f0f8e3ecdddc3982012a85839e8e46041deba1cf22f61292f47a20538eb089180196b2ebf4e0cc1da106c7c5b3dc7264c5ef26f48dbfacd3cc854cc64a345d08359f2ff539449d1d221930626e8df9969275b961a22b32ebab4cebf3dbf963bb25ef663258cf00d35d076aad9adabae4d0573f4c37e058


I'm trying to do something like this.
I done this in Java with class BigInteger, but cannot do it in JavaCard.
I know how to do mod but cannot multiple 2big numbers

roundtable
Posts: 18
Joined: Mon Sep 18, 2017 9:52 pm
Points :240
Contact:

Re: Multiply big numbers

Post by roundtable » Wed Apr 18, 2018 10:14 pm

You should know something important about javacard:
1. javacard is the mini subset of standard Java, so most of features, packages and classes are not supported in javacard. For example , class BigInterger, it is only available on standard Java (JDK) , if you use it on javacad, you can't build it successfully.

2. javacard is run on limited resource (RAM,eeprom) smartcad IC, if you implement your big number calculation using normal operation just lIke on x86,where algorithm in elementary school is used. the performance is terrible and complicated.

Instead, some javacard vendor has done it, providing special their private javacrd API to accelerate those big integer arithmetic via smartcard IC coprocessor, based on that, you can implement your own customized algorithm, such as gen prime, inverse ....

I

djordjem
Posts: 5
Joined: Fri Dec 22, 2017 5:59 am
Points :442
Contact:

Re: Multiply big numbers

Post by djordjem » Thu Apr 19, 2018 8:36 am

roundtable wrote:You should know something important about javacard:
1. javacard is the mini subset of standard Java, so most of features, packages and classes are not supported in javacard. For example , class BigInterger, it is only available on standard Java (JDK) , if you use it on javacad, you can't build it successfully.

2. javacard is run on limited resource (RAM,eeprom) smartcad IC, if you implement your big number calculation using normal operation just lIke on x86,where algorithm in elementary school is used. the performance is terrible and complicated.

Instead, some javacard vendor has done it, providing special their private javacrd API to accelerate those big integer arithmetic via smartcard IC coprocessor, based on that, you can implement your own customized algorithm, such as gen prime, inverse ....

I


I know all of this thing. I try to implement PACE protocol in passport applet and one of things is to multiply two big numbers. I am working with RSA keys and i must calculate (G^s * h) mod P where G = 128 byte array, s = 16 byte array and h = 128 byte array, p = 128 byte array. Formula that i use for multiply is:
a = (G^s mod P)
b = h mod P
((a + b)^2 mod P - a^2 mod P - b^2 mod P) / 2 = a * b
For square and mod i am using doFinal method from RSA Chipper.

wumindejia
Posts: 55
Joined: Thu Sep 22, 2016 5:05 am
Points :784
Contact:

Re: Multiply big numbers

Post by wumindejia » Thu Apr 19, 2018 9:38 pm

Sorry ! The jmrtd call a class of java.math.BigInteger.

Post Reply Previous topicNext topic

Who is online

Users browsing this forum: No registered users and 44 guests

JavaCard OS : Disclaimer