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The LSAPR_ACCOUNT_INFORMATION structure specifies a security principal security identifier (SID).

 typedef struct _LSAPR_ACCOUNT_INFORMATION {
   PRPC_SID Sid;
 } LSAPR_ACCOUNT_INFORMATION,
  *PLSAPR_ACCOUNT_INFORMATION;

Sid: This field contains the SID of the security principal. This field MUST NOT be NULL.