Crypt::IDA is a Perl module that implements Rabin's Information Dispersal Algorithm. This is what's known as a "threshold system": a secret is divided into n shares with the property that any k (the "quorum" or "threshold") of those shares (with k <= n) can be combined at a later time to reconstruct the secret. The algorithm should be cryptographically secure in the sense that if fewer shares than the quorum k are presented, no information about the secret is revealed. The module uses Math::FastGF2 to efficiently implement the algorithm, making it suitable for securely sharing and distributing even large files. The Crypt::IDA::ShareFile module implements a file format for creating, storing, and distributing shares created with Crypt::IDA.