A question about distribute storage keys

[congling]

Hi Mr Richard,     For some reason, I was about to programme for a "distributed storage" for a private key.     But I have no idea about how can do this.     This is my problem:         There are 6 people can hold the private key. When four of them meet together, they can     restore the private key. But if less than 4, private key are still  unable to restore, and     the difficulty to get the key is almost the same to nobody involve.        ( The private key is the RSA key.)         Can you help me or give me some idea?         Thank you. Regards, Congling