What Is the Primary Security Assumption for an SPV Client?

The primary security assumption is that the majority of the network's full nodes are honest and will not collude to present a false block header with a tampered Merkle Root. An SPV client trusts the block header it receives from a full node, relying on the difficulty of the PoW to secure that header's integrity against fraudulent inclusion of a transaction.

What Is the Fundamental Difference between a Full Node and an SPV Client in a Blockchain Network?
How Does an SPV Wallet Trust the Block Headers It Receives?
How Do ‘Simplified Payment Verification’ (SPV) Wallets Use Merkle Trees?
How Does the Reduced Security of an SPV Client Manifest Compared to a Full Node?
How Do “Checkpoints” Enhance the Security of SPV Clients?
Why Are Full Nodes Still Necessary for the Network When SPV Exists?
How Does the Time Value of Money Factor into a Miner’s Decision to Broadcast a Block?
What Is the “Byzantine Generals Problem” That pBFT Aims to Solve?

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