Abstract: The disclosed computer-implemented method for verifying connection integrity may include (i) receiving a request from a client to initiate a connection to a server via a middlebox, (ii) receiving, from the client, via a side protocol executing in parallel with a transport layer security protocol, a request for a certificate for the middlebox, (iii) sending, to the client, via the side protocol, the certificate, (iv) receiving, from the client, via the side protocol, a request for an additional certificate from a device upstream of the middlebox, (v) requesting, from the device upstream of the middlebox, via the side protocol, the additional certificate, (vi) receiving, from the device upstream of the middlebox, via the side protocol, the additional certificate, (vii) sending, to the client, via the side protocol, the additional certificate, and (viii) relaying data via the connection. Various other methods, systems, and computer-readable media are also disclosed.