I want to connect to a server with PSK-TLS without the use of certificates, but when it attempts to send the client key exchange after saying hello to the openssl server it fails with 'bad record / mac' from the server side which the guys at OpenSSL say is an issue with the encryption on the client side. This is my code: nw_parameters_configure_protocol_block_t configure_tls = ^(nw_protocol_options_t tls_options) { sec_protocol_options_t sec_options = nw_tls_copy_sec_protocol_options(tls_options); dispatch_data_t psk = dispatch_data_create("abc123", 6, nil, DISPATCH_DATA_DESTRUCTOR_DEFAULT); dispatch_data_t client_id = dispatch_data_create("test", 4, nil, DISPATCH_DATA_DESTRUCTOR_DEFAULT); sec_protocol_options_set_min_tls_protocol_version(sec_options, tls_protocol_version_TLSv12); sec_protocol_options_set_tls_max_version(sec_options, tls_protocol_version_TLSv12); sec_protocol_options_add_tls_ciphersuite(sec_options, (SSLCipherSuite)TLS_PSK_WITH_AES_256_GCM_SHA384); sec_protocol_options_set_tls_ocsp_enabled(sec_options, false); sec_protocol_options_set_tls_sct_enabled(sec_options, false); sec_protocol_options_set_peer_authentication_required(sec_options, true); sec_protocol_options_set_tls_renegotiation_enabled(sec_options, true); sec_protocol_options_set_tls_tickets_enabled(sec_options, true); sec_protocol_options_set_tls_resumption_enabled(sec_options, true); sec_protocol_options_add_pre_shared_key(sec_options, psk, client_id); }; nw_parameters_t parameters = nw_parameters_create_secure_tcp(configure_tls, NW_PARAMETERS_DEFAULT_CONFIGURATION); nw_endpoint_t endpoint = nw_endpoint_create_host("192.168.0.29", "8888"); nw_connection_t connection = nw_connection_create(endpoint, parameters); nw_connection_set_state_changed_handler(connection, ^(nw_connection_state_t state, nw_error_t error) { switch (state) { case nw_connection_state_waiting: NSLog(@"waiting"); break; case nw_connection_state_failed: NSLog(@"failed"); break; case nw_connection_state_ready: NSLog(@"connection is ready"); break; case nw_connection_state_cancelled: NSLog(@"connection is cancelled"); break; default: NSLog(@"other"); break; } }); nw_connection_set_queue(connection, dispatch_get_main_queue()); nw_connection_start(connection); I'm using the OpenSSL server to establish the connection with the command: openssl3 s_server -tls1_2 -accept 8888 -nocert -psk abc123 -psk_identity test -cipher PSK-AES128-GCM-SHA384 I've tested the connection works using: openssl3 s_client -tls1_2 -connect localhost:8888 -psk abc123 -psk_identity test -cipher PSK-AES128-GCM-SHA384 But for some reason it always fails when trying to do the iOS network.framework equivilant. I've tried with a number of ciphersuites that use PSK too so it doesn't seem to be that it is because of i.e. a deprecated ciphersuite.

It looks like your code is passing the client/server hello and failing when it attempts to decrypt, I had similar issues when I found that OpenSSL specified the PSK in hex rather than plaintext so I got this issue, but on iOS side I'm not entirely sure of the format in which we should be passing the PSK because it still seems to be failing for me. So everything else other than the PSK is probably configured correctly.

Same issue Xcode 15.1 and iPhone 12 (iOS 17.2)