I am sure you have watched many of those sci-fi or crime movies where a safe can be unlocked only if many people enter their keys into the safe and turn them simultaneously. If even one key is missing, it becomes impossible to open the safe door and others helplessly try to find the missing key. Well those kind of safes exist, but they are very expensive. While you can lock just about anything in the safe, but if you want to lock your text message then you do not really need a safe. If you want to hide your text message, then you can use the free and open source Secret Sharp utility. It encrypts text messages and generates a number of shares (passwords). The encrypted message is decrypted only if all the shared keys are added in the program.
You can get the Secret Sharp program from its sourceForge website. The program comes in an installable MSI package. It is coded using the .NET 2.0 framework, so you may have to install .NET 2.0 redistributable on your system first.
The program offers two options when you launch it – create shares or combine shares. If you are going to encrypt a text message and generate shares, then you have to select Create Shares.
You can choose how many shares you want to create. It depends how many people are going to have these shares. If you want the message to be protected by 5 people, then you have to generate 5 shares. You can also make it easy for the message to decrypt by decreasing the number of shares needed to decrypt the message.
Then you can type in your text message which you want to encrypt. Instead of a secret text message, you can also encrypt a passphrase that you would use elsewhere.
In the end it generates the number of shares that you asked for – showing one share per line of the text. You can copy and save them to a text file or distribute the shares among the group of people that would be able to decrypt the original secret text jointly.
If later you want to decrypt the secret text message, then all the people in the group will have to insert their shares to rebuild the secret. Depending on your encryption parameters, you may not have to enter all the shares.
The secret message is decrypted only if you enter correct and required number of shares. The decrypted secret message is displayed in the window which you can copy or save to your hard disk.
Conclusion: If you want to protect a passphrase or secret message in such a way that it can be unlocked by combining all the shares possessed by different persons, then Secret Sharp is for you. It can encrypt text message and generate multiple shares or keys all of which have to be used in order to decrypt the encrypted message.
You can download the Secret Sharp from http://sourceforge.net/projects/secretsharp/.