Help for IBE programsBen Lynn (blynn@cs.stanford.edu)INTRODUCTIONTwo binaries are provided, one to generate system parameters, and the otherto perform IBE operations.QUICKSTARTThe default configuration should be fine.Encrypt messages to yourself by typingibe encrypt IDwhere ID is your email address. (Throughout this section, ID will alwaysbe your email address.)It uses standard input/output, so you can encrypt a file by typingsomething like:ibe encrypt ID < plain.txt > cipher.txtBy now it is evident what the main advantage of IBE is: there is no needto generate/retrieve a public key in order to encrypt.Next, retrieve your private key share by typing:ibe request IDYou'll be asked to make up a password.Soon you should receive an email from the private key generator to thataddress. Save it to a file "keyshare". Then type:ibe combine ID keyshareYou'll need the password you just made up for this to work, and it willthen ask you for another password.Now you can decrypt the message you encrypted to yourself by typing:ibe decrypt ID < cipher.txt(You'll need to enter the password for your private key which you concoctedin the previous step.)You should also be able to decrypt the message sent to you on the IBEhomepage (in the Try IBE section).DETAILSConfigure the system parameters generator, gen, by editing gen.cnf.If run, it will output a file containing new system parameters and secretshares for PKG's to use.Configure ibe by editing ibe.cnf. To use the program, typeibe <command> <args>on the command-line. At the moment the commands are:encrypt    Once system parameters are available (they can be generated by the gen    program or obtained elsewhere), the encrypt command can be used (recall    in an IBE scheme, any string is a public key). So for example, typing:    ibe encrypt Alice    will encrypt the standard input using the public key "Alice".    The ciphertext is printed on standard output.request    The request command requests the private key for a given ID.    For example,    ibe request Bob@foo.bar    will send the server(s) (configured in ibe.cnf) requests for parts of    Bob's private key. They will be emailed to the address provided on the    command-line (i.e. the ID).combine    The combine command combines files given out by private key generators into    a private key. For example, if Bob has received the file "file" from a PKG,    and only one file is needed to make a private key (this depends on the    system parameters), he can type    ibe combine Bob@foo.bar file    to recover his private key. If there were more than one file, he types    ibe combine Bob@foo.bar file1 file2 ...decrypt    Once the private key has been recovered (it is saved to a file    automatically; the filename is read from the config file),    the decrypt command may be used as follows:    ibe decrypt Alice    It takes the ciphertext on standard input and outputs the corresponding    plaintext on standard output.extract_share        This simulates what a PKG would do. If you have run gen to obtain    a master share, then run    ibe extract_share Alice mastersharefile    to obtain a key share for Alice corresponding to the given master share.    These key shares can be combined with the combine command to construct    a private key.key_from_master_shares    This is intended for testing only; in real life, the master shares should    never reside on the same server. Type    ibe key_from_master_shares Alice mastersharefile1 mastersharefile2 ...    to recover Alice's private key.imratio    The imratio command is a benchmarking tool, which was used to find the    relative cost of inversions and multiplications. It is not needed by the    end user, but I'm interested in what values various machines report for    the I/M ratios.