what is ISD

[takakiyo]

Hi, I am confused about ISD(Issuer Security Domain) of GP, could you explain to me?
Q1: ISD is used to do what
Q2: i have to use ISD if i install applet？

[UNKNwYSHSA]

Security Domains hold cryptographic keys which can be used to support Secure Channel Protocol operations and/or to authorize card content management functions (supported by GlobalPlatform Environment (OPEN)).
And the Issuer Security Domain has special characteristics from other SD, described in "7.1.1 Issuer Security Domain" of "GlobalPlatform Card Specification 2.2.1".

For question1:
1 You can send GP command to SDs (ISD or other SDs) to perform GP operation;
2 You can install Applet use SDs (ISD or other SDs);