This is a symmetric encryption algorithm for use in applications like protecting the secrecy of blockchain contents where the encryption needs to be very strong. The algorithm has these properties:

• It is necessary to decrypt the entire text at once, rather than decrypt in pieces, as with a block cypher.
• The key can as as long as the plaintext message or longer.
• All wrong plain texts the same length as the correct plain text can be generated by wrong keys. This Ensures that too many plausible plaintext's that can be generated to tell by brute force which is the correct one.

The encryption algorithm is very simple:

1. If the plaintext is longer then the key, fail.
2. If the plaintext is shorter than the key, pad it to the length of the key with null bytes (0).
3. XOR the key with the padded plain text. The result is the encrypted text.

The decryption algorithm is the same.

Each plaintext that is encrypted should be encrypted with a different key. If it is known that two encrypted texts were encrypted with the same key, then it becomes easier to guess the key. For this reason, the crypto-shuffle library includes a RandomKeyGenerator class to generate random keys.

The most secure way to share the key to decrypt a message is to keep it somewhere different than the encrypted message. However this creates the challenge of creating a mechanism to manage all of the random key and keeping track of which key goes with which encrypted text. The inconvenience of having to do this may be unacceptable.

If the encrypted message is stored on a blockchain, it may be considered convenient to store the crypto-shuffle key on the same blockchain. In these cases, it is recommended that the key be encrypted with the public keys of the parties that you want to share the plaintext with.

The crypto-shuffle package includes a convenient mechanism for creating a single JSON object that contains versions of crypto-shuffle keys encrypted by each of a set of public keys. This is the MultiEncryption class.

To create a MultiEncryption object, you pass the constructor a plain text crypto-shuffle key and a collection of one or more public keys. The constructed object contains versions of the crypto-shuffle key encrypted by each of the public keys.

To decrypt the contents of a MultiEncryption object, pass a public key and its corresponding private key to the MultiEncryption object’s decrypt method. If the MultiEncryption object contains an encrypted crypto-shuffle key that was encrypted with the given public key, it uses the corresponding private key to decrypt the crypto-shuffle key.

You can generate a JSON representation of a MultiEncryption object by calling its toJson method. Provide JSON version of the MultiEncryption object as a field value in the same transaction as you have encrypted values. If someone wants to convert the JSON into a MultiEncryption object, they can pass the JSON to the static method MultiEncryption.fromJson.

Sharing keys through a means outside of the blockchain is the most secure way to share keys.

Note: This version of cryptoshuffle is not compatible with previous versions.