# Data Availability Certificates (DACerts)

A fundamental concept within AnyTrust is the Data Availability Certificate (DACert). A DACert encompasses the hash of a data block, an expiration time, and proof that N-1 Committee members have signed the (hash, expiration time) pair. This proof includes the hash of the Keyset used for signing, a bitmap indicating which Committee members signed, and a BLS aggregated signature over the BLS12-381 curve, attesting to the signatories.

Due to the 2-of-N trust assumption, a DACert serves as evidence that a block's data will be accessible from at least one honest Committee member until the specified expiration time. This trust assumption underpins the reliability and security of data availability within the AnyTrust framework.


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