Block chain data writing and accessing method and device

The embodiment of the invention provides a block chain data writing and accessing method and device, which are used for improving the safety of block chain data storage and accessing and can save the system bandwidth at the same time. The method comprises the steps that each consensus node obtains a data writing request sent by a data owner, wherein each data write-in request comprises the same target encrypted data and different key shares, the target encrypted data is obtained by the data owner through carrying out authentication encryption processing on plaintext data according to a target key, and the target encrypted data comprises ciphertext data and data authentication information; each secret key share is obtained by splitting the target secret key by the data owner through a secret sharing mechanism; each consensus node performs consensus processing on the target encrypted data; and after determining that a consensus is reached for the target encrypted data, the obtained target encrypted data and the