Blockstack PBC has a draft of whitepaper 2.0 that is currently being reviewed by relevant experts. Stacks Improvement Proposals (SIPs) for the new consensus algorithm and smart contract language are respectively available as SIP-001 and SIP-002.
The Blockstack technology has evolved considerably in the past two years and the papers below don’t fully reflect the current decentralized computing stack.
Blockstack: A New Decentralized Internet
Whitepaper Version 1.1 - Oct 2017
Blockstack Token Whitepaper
Token Whitepaper Version 1.2 - Oct 2017