WHAT: Simplified Payment Verification (SPV) does two basic things:
A) Ensures: that transactions are in a block
B) Confirms: that additional blocks are being added to the blockchain. (R2)
WHY: SPV allows a user to verify that a transaction is in the Bitcoin blockchain, without running a full node. A lightweight SPV client only needs the block headers of the longest chain instead of full blocks.
To verify that a transaction is in a block, a SPV client requests proof in the form of a Merkle branch. “Linking the transaction to a place in the active chain demonstrates that a network node has accepted it, and blocks added after it further establish confirmation.” (R1)
REFERENCES:
(1) https://en.bitcoinwiki.org/wiki/Simplified_Payment_Verification
(2) https://medium.com/@jonaldfyookball/why-every-bitcoin-user-should-understand-spv-security-520d1d45e0b9
Pic: Photo by Nathan Bingle on Unsplash