JavacardOS will not accept order any more, please contact our partner Feitian online Store:
https://ftsafe.en.alibaba.com/index.html

Why the byte length of KeyAgreement.generateSecret() is 20

JavaCard Applet Development Related Questions and Answers.
Post Reply Previous topicNext topic
DaHuFa
Posts: 53
Joined: Mon Jun 04, 2018 5:07 am
Points :392
Contact:
Contact DaHuFa

Why the byte length of KeyAgreement.generateSecret() is 20

Post by DaHuFa » Fri Jul 13, 2018 5:10 am

Hello,
I write a applet to implement KeyAgreement recently. I create a 256 bits EC key, then call KeyAgreement.generateSecret(). In the end, the length of result is 20 bytes. Why? My EC key length is 256 bits, 32 bytes. Why my result length is 20 bytes?
Top
happy123654
Posts: 35
Joined: Wed Jun 20, 2018 4:06 am
Points :218
Contact:
Contact happy123654

Re: Why the byte length of KeyAgreement.generateSecret() is 20

Post by happy123654 » Fri Jul 13, 2018 5:12 am

Because the function implements SHA_1 calculation in the last step.
Top
DaHuFa
Posts: 53
Joined: Mon Jun 04, 2018 5:07 am
Points :392
Contact:
Contact DaHuFa

Re: Why the byte length of KeyAgreement.generateSecret() is 20

Post by DaHuFa » Fri Jul 13, 2018 5:29 am

But my sample card which installed other's applet return 32 bytes. I think there maybe something I don't know....
Top
BirdKing
Posts: 86
Joined: Wed Nov 04, 2015 7:23 am
Points :656
Contact:
Contact BirdKing

Re: Why the byte length of KeyAgreement.generateSecret() is 20

Post by BirdKing » Fri Jul 13, 2018 5:42 am

The sample applet maybe use ALG_EC_SVDP_DH_PLAIN.
Top
Post Reply Previous topicNext topic

Return to “Questions & Answers”

Who is online

Users browsing this forum: No registered users and 66 guests

JavaCard OS : Disclaimer