Listing 2. CAS+ definition for data retrieval process (with consent).

protocol data_retrieval_consent;

identifiers

VO, B, A  : user;

Data     : number;

Ks      : symmetric_key;

Kp      : public_key;

messages

1. B -> VO   : {Ks}Kp

2. B -> VO   : {Data}Ks

3. VO-> A    : Data

knowledge

B  : Data,Kp,Ks;

session_instances

[VO:vo,B:b,A:a,Data:d,Ks:ks,Kp:kp];

intruder_knowledge

vo,b,kp;

goals

secrecy_of Data