Bandwidth offers TLS/SRTP for voice traffic, including inbound and outbound calling. Currently, we require our customers to use TLS version 1.2.

TLS/SRTP specifications:
Supported TLS version	1.2
TLS key pair type	RSA (ECC certificates are not supported)
Supported TLS cipher suites	RSA_WITH_AES_128_CBC_SHA (default) RSA_WITH_AES_128_CBC_SHA_256 RSA_WITH_AES_256_CBC_SHA_256 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (requires SIP AUTH for outbound traffic) TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (requires SIP AUTH for outbound traffic)
Supported SRTP cipher suites	AES_CM_128_HMAC_SHA1_80

More information can be found here: Bandwidth TLS/SRTP Support

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