IMPORTANT: In the special case that a signature is being provided for a key used to authorize a precompiled contract, the pubKeyPrefix must contain the entire public key! That is, if the key is a Ed25519 key, the pubKeyPrefix should be 32 bytes long. If the key is a ECDSA(secp256k1) key, the pubKeyPrefix should be 33 bytes long, since we require the compressed form of the public key.
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