View Source ExLibSRTP.Policy (ExLibSRTP v0.7.2)
Policy for setting up SRTP stream configuration.
For meaning of particular fields maps to the fields of srtp_policy_t C struct found in libSRTP.
It is described in srtp.h header
Here's a brief description:
:ssrc- Either an accepted SSRC or atoms mapping toSSRC_ANY_(INBOUND/OUTBOUND)flags:key- a master key for encrpytion:rtp- crypto profile defining a policy for RTP encryption:rtcp- crypto profile defining a policy for RTCP encryption:windows_size- the sequence number window size used for replay protection As the comment here says, it must be at least 64 and any value above 2^15 (32768) won't be effective as explained here. The default value is 128:allow_repeat_tx- if true, packet with repeated sequence number won't cause an error. Note that unless the RTP payload is the same it may introduce a severe security weakness.
Summary
Types
@type crypto_profile_t() ::
:rtp_default
| :rtcp_default
| :aes_cm_128_hmac_sha1_80
| :aes_cm_128_hmac_sha1_32
| :aes_cm_128_null_auth
| :null_cipher_hmac_sha1_80
| :null_cipher_hmac_null
| :aes_cm_256_hmac_sha1_80
| :aes_cm_256_hmac_sha1_32
| :aes_cm_256_null_auth
| :aes_cm_192_hmac_sha1_80
| :aes_cm_192_hmac_sha1_32
| :aes_cm_192_null_auth
| :aes_gcm_128_8_auth
| :aes_gcm_256_8_auth
| :aes_gcm_128_8_only_auth
| :aes_gcm_256_8_only_auth
| :aes_gcm_128_16_auth
| :aes_gcm_256_16_auth
@type key_spec_t() :: binary() | [ExLibSRTP.MasterKey.t()]
@type ssrc_pattern_t() :: ExLibSRTP.ssrc_t() | :any_inbound | :any_outbound
@type t() :: %ExLibSRTP.Policy{ allow_repeat_tx: boolean(), key: key_spec_t(), rtcp: crypto_profile_t(), rtp: crypto_profile_t(), ssrc: ssrc_pattern_t(), window_size: 64..32768 | :default }
Functions
@spec crypto_profile_from_dtls_srtp_protection_profile( value :: pos_integer() | {pos_integer(), pos_integer()} ) :: {:ok, crypto_profile_t()} | {:error, :unsupported_crypto_profile}
Relevant specification: https://www.iana.org/assignments/srtp-protection/srtp-protection.xhtml