Secure Frame (SFrame)

4.1. Application Context

SFrame is a general encryption framing, intended to be used as an E2E encryption layer over an underlying HBH-encrypted transport such as SRTP or QUIC [RFC3711][I-D.ietf-moq-transport].¶

The scale at which SFrame encryption is applied to media determines the overall amount of overhead that SFrame adds to the media stream, as well as the engineering complexity involved in integrating SFrame into a particular environment. Two patterns are common: Either using SFrame to encrypt whole media frames (per-frame) or individual transport-level media payloads (per-packet).¶

For example, Figure 1 shows a typical media sender stack that takes media in from some source, encodes it into frames, divides those frames into media packets, and then sends those payloads in SRTP packets. The receiver stack performs the reverse operations, reassembling frames from SRTP packets and decoding. Arrows indicate two different ways that SFrame protection could be integrated into this media stack, to encrypt whole frames or individual media packets.¶

Applying SFrame per-frame in this system offers higher efficiency, but may require a more complex integration in environments where depacketization relies on the content of media packets. Applying SFrame per-packet avoids this complexity, at the cost of higher bandwidth consumption. Some quantitative discussion of these trade-offs is provided in Appendix C.¶

As noted above, however, SFrame is a general media encapsulation, and can be applied in other scenarios. The important thing is that the sender and receivers of an SFrame-encrypted object agree on that object's semantics. SFrame does not provide this agreement; it must be arranged by the application.¶

Like SRTP, SFrame does not define how the keys used for SFrame are exchanged by the parties in the conference. Keys for SFrame might be distributed over an existing E2E-secure channel (see Section 5.1), or derived from an E2E-secure shared secret (see Section 5.2). The key management system MUST ensure that each key used for encrypting media is used by exactly one media sender, in order to avoid reuse of IVs.¶

4.2. SFrame Ciphertext

An SFrame ciphertext comprises an SFrame header followed by the output of an AEAD encryption of the plaintext [RFC5116], with the header provided as additional authenticated data (AAD).¶

The SFrame header is a variable-length structure described in detail in Section 4.3. The structure of the encrypted data and authentication tag are determined by the AEAD algorithm in use.¶

When SFrame is applied per-packet, the payload of each packet will be an SFrame ciphertext. When SFrame is applied per-frame, the SFrame ciphertext representing an encrypted frame will span several packets, with the header appearing in the first packet and the authentication tag in the last packet.¶

4.3. SFrame Header

The SFrame header specifies two values from which encryption parameters are derived:¶

• A Key ID (KID) that determines which encryption key should be used¶
• A counter (CTR) that is used to construct the IV for the encryption¶

Applications MUST ensure that each (KID, CTR) combination is used for exactly one encryption operation. A typical approach to achieving this gaurantee is outlined in Section 9.1.¶

Both the counter and the key id are encoded as integers in network (big-endian) byte order, in a variable length format to decrease the overhead. The length of each field is up to 8 bytes and is represented in 3 bits in the SFrame header: 000 represents a length of 1, 001 a length of 2, etc.¶

The first byte in the SFrame header has a fixed format and contains the header metadata:¶

Reserved (R, 1 bit):

This field MUST be set to zero on sending, and MUST be ignored by receivers.¶

Counter Length (LEN, 3 bits):

This field indicates the length of the CTR field in bytes, minus one (the range of possible values is thus 1-8).¶

Extended Key Id Flag (X, 1 bit):

Indicates if the key field contains the key id or the key length.¶

Key or Key Length (K, 3 bits):

This field contains the key id (KID) if the X flag is set to 0, or the key length (KLEN) if set to 1.¶

If X flag is 0, then the KID is in the range of 0-7 and the counter (CTR) is found in the next LEN bytes:¶

If X flag is 1 then KLEN is the length of the key (KID) in bytes, minus one (the range of possible lengths is thus 1-8). The KID is encoded in the KLEN bytes following the metadata byte, and the counter (CTR) is encoded in the next LEN bytes:¶

4.4. Encryption Schema

SFrame encryption uses an AEAD encryption algorithm and hash function defined by the cipher suite in use (see Section 4.5). We will refer to the following aspects of the AEAD algorithm below:¶

• AEAD.Encrypt and AEAD.Decrypt - The encryption and decryption functions for the AEAD. We follow the convention of RFC 5116 [RFC5116] and consider the authentication tag part of the ciphertext produced by AEAD.Encrypt (as opposed to a separate field as in SRTP [RFC3711]).¶
• AEAD.Nk - The size in bytes of a key for the encryption algorithm¶
• AEAD.Nn - The size in bytes of a nonce for the encryption algorithm¶
• AEAD.Nt - The overhead in bytes of the encryption algorithm (typically the size of a "tag" that is added to the plaintext)¶

def derive_key_salt(KID, base_key):
  sframe_secret = HKDF-Extract("SFrame 1.0 Secret " + KID, base_key)
  sframe_key = HKDF-Expand(sframe_secret, "key", AEAD.Nk)
  sframe_salt = HKDF-Expand(sframe_secret, "salt", AEAD.Nn)
  return sframe_key, sframe_salt

def encrypt(CTR, KID, metadata, plaintext):
  sframe_key, sframe_salt = key_store[KID]

  ctr = encode_big_endian(CTR, AEAD.Nn)
  nonce = xor(sframe_salt, CTR)

  header = encode_sframe_header(CTR, KID)
  aad = header + metadata

  ciphertext = AEAD.Encrypt(sframe_key, nonce, aad, plaintext)
  return header + ciphertext

def decrypt(metadata, sframe_ciphertext):
  KID, CTR, ciphertext = parse_ciphertext(sframe_ciphertext)

  sframe_key, sframe_salt = key_store[KID]

  ctr = encode_big_endian(CTR, AEAD.Nn)
  nonce = xor(sframe_salt, ctr)
  aad = header + metadata

  return AEAD.Decrypt(sframe_key, nonce, aad, ciphertext)

4.5. Cipher Suites

Each SFrame session uses a single cipher suite that specifies the following primitives:¶

• A hash function used for key derivation¶
• An AEAD encryption algorithm [RFC5116] used for frame encryption, optionally with a truncated authentication tag¶

This document defines the following cipher suites, with the constants defined in Section 4.4:¶

Numeric identifiers for these cipher suites are defined in the IANA registry created in Section 8.1.¶

In the suite names, the length of the authentication tag is indicated by the last value: "_128" indicates a hundred-twenty-eight-bit tag, "_80" indicates a eighty-bit tag, "_64" indicates a sixty-four-bit tag and "_32" indicates a thirty-two-bit tag.¶

In a session that uses multiple media streams, different cipher suites might be configured for different media streams. For example, in order to conserve bandwidth, a session might use a cipher suite with eighty-bit tags for video frames and another cipher suite with thirty-two-bit tags for audio frames.¶

def derive_subkeys(sframe_key):
  tag_len = encode_big_endian(Nt, 8)
  aead_label = "SFrame 1.0 AES CTR AEAD " + tag_len
  aead_secret = HKDF-Extract(aead_label, sframe_key)
  enc_key = HKDF-Expand(aead_secret, "enc", Nk)
  auth_key = HKDF-Expand(aead_secret, "auth", Nh)
  return enc_key, auth_key

def compute_tag(auth_key, nonce, aad, ct):
  aad_len = encode_big_endian(len(aad), 8)
  ct_len = encode_big_endian(len(ct), 8)
  tag_len = encode_big_endian(Nt, 8)
  auth_data = aad_len + ct_len + tag_len + nonce + aad + ct
  tag = HMAC(auth_key, auth_data)
  return truncate(tag, Nt)

def AEAD.Encrypt(key, nonce, aad, pt):
  enc_key, auth_key = derive_subkeys(key)
  ct = AES-CTR.Encrypt(enc_key, nonce, pt)
  tag = compute_tag(auth_key, nonce, aad, ct)
  return ct + tag

def AEAD.Decrypt(key, nonce, aad, ct):
  inner_ct, tag = split_ct(ct, tag_len)

  enc_key, auth_key = derive_subkeys(key)
  candidate_tag = compute_tag(auth_key, nonce, aad, inner_ct)
  if !constant_time_equal(tag, candidate_tag):
    raise Exception("Authentication Failure")

  return AES-CTR.Decrypt(enc_key, nonce, inner_ct)

5.1. Sender Keys

If the participants in a call have a pre-existing E2E-secure channel, they can use it to distribute SFrame keys. Each client participating in a call generates a fresh encryption key. The client then uses the E2E-secure channel to send their encryption key to the other participants.¶

In this scheme, it is assumed that receivers have a signal outside of SFrame for which client has sent a given frame (e.g., an RTP SSRC). SFrame KID values are then used to distinguish between versions of the sender's key.¶

Key IDs in this scheme have two parts, a "key generation" and a "ratchet step". Both are unsigned integers that begin at zero. The key generation increments each time the sender distributes a new key to receivers. The "ratchet step" is incremented each time the sender ratchets their key forward for forward secrecy:¶

sender_base_key[i+1] = HKDF-Expand(
                         HKDF-Extract("SFrame 1.0 Ratchet", sender_base_key[i]),
                         "", CipherSuite.Nh)

For compactness, we do not send the whole ratchet step. Instead, we send only its low-order R bits, where R is a value set by the application. Different senders may use different values of R, but each receiver of a given sender needs to know what value of R is used by the sender so that they can recognize when they need to ratchet (vs. expecting a new key). R effectively defines a re-ordering window, since no more than 2^R ratchet steps can be active at a given time. The key generation is sent in the remaining 64 - R bits of the key ID.¶

KID = (key_generation << R) + (ratchet_step % (1 << R))

The sender signals such a ratchet step update by sending with a KID value in which the ratchet step has been incremented. A receiver who receives from a sender with a new KID computes the new key as above. The old key may be kept for some time to allow for out-of-order delivery, but should be deleted promptly.¶

If a new participant joins mid-call, they will need to receive from each sender (a) the current sender key for that sender and (b) the current KID value for the sender. Evicting a participant requires each sender to send a fresh sender key to all receivers.¶

5.2. MLS

The Messaging Layer Security (MLS) protocol provides group authenticated key exchange [I-D.ietf-mls-architecture] [I-D.ietf-mls-protocol]. In principle, it could be used to instantiate the sender key scheme above, but it can also be used more efficiently directly.¶

MLS creates a linear sequence of keys, each of which is shared among the members of a group at a given point in time. When a member joins or leaves the group, a new key is produced that is known only to the augmented or reduced group. Each step in the lifetime of the group is know as an "epoch", and each member of the group is assigned an "index" that is constant for the time they are in the group.¶

To generate keys and nonces for SFrame, we use the MLS exporter function to generate a base_key value for each MLS epoch. Each member of the group is assigned a set of KID values, so that each member has a unique sframe_key and sframe_salt that it uses to encrypt with. Senders may choose any KID value within their assigned set of KID values, e.g., to allow a single sender to send multiple uncoordinated outbound media streams.¶

base_key = MLS-Exporter("SFrame 1.0 Base Key", "", AEAD.Nk)

For compactness, we do not send the whole epoch number. Instead, we send only its low-order E bits, where E is a value set by the application. E effectively defines a re-ordering window, since no more than 2^E epochs can be active at a given time. Receivers MUST be prepared for the epoch counter to roll over, removing an old epoch when a new epoch with the same E lower bits is introduced.¶

Let S be the number of bits required to encode a member index in the group, i.e., the smallest value such that group_size < (1 << S). The sender index is encoded in the S bits above the epoch. The remaining 64 - S - E bits of the KID value are a context value chosen by the sender (context value 0` will produce the shortest encoded KID).¶

KID = (context << (S + E)) + (sender_index << E) + (epoch % (1 << E))

Once an SFrame stack has been provisioned with the sframe_epoch_secret for an epoch, it can compute the required KIDs and sender_base_key values on demand, as it needs to encrypt/decrypt for a given member.¶

6.1. Selective Forwarding Units

Selective Forwarding Units (SFUs) (e.g., those described in Section 3.7 of [RFC7667]) receive the media streams from each participant and select which ones should be forwarded to each of the other participants. There are several approaches about how to do this stream selection but in general, in order to do so, the SFU needs to access metadata associated to each frame and modify the RTP information of the incoming packets when they are transmitted to the received participants.¶

This section describes how this normal SFU modes of operation interacts with the E2EE provided by SFrame¶

6.2. Video Key Frames

Forward and Post-Compromise Security requires that the e2ee keys are updated anytime a participant joins/leave the call.¶

The key exchange happens asynchronously and on a different path than the SFU signaling and media. So it may happen that when a new participant joins the call and the SFU side requests a key frame, the sender generates the e2ee encrypted frame with a key not known by the receiver, so it will be discarded. When the sender updates his sending key with the new key, it will send it in a non-key frame, so the receiver will be able to decrypt it, but not decode it.¶

Receiver will re-request an key frame then, but due to sender and SFU policies, that new key frame could take some time to be generated.¶

If the sender sends a key frame when the new e2ee key is in use, the time required for the new participant to display the video is minimized.¶

6.3. Partial Decoding

Some codes support partial decoding, where it can decrypt individual packets without waiting for the full frame to arrive, with SFrame this won't be possible because the decoder will not access the packets until the entire frame has arrived and was decrypted.¶

7.1. No Per-Sender Authentication

SFrame does not provide per-sender authentication of media data. Any sender in a session can send media that will be associated with any other sender. This is because SFrame uses symmetric encryption to protect media data, so that any receiver also has the keys required to encrypt packets for the sender.¶

7.2. Key Management

Key exchange mechanism is out of scope of this document, however every client SHOULD change their keys when new clients joins or leaves the call for "Forward Secrecy" and "Post Compromise Security".¶

7.3. Authentication tag length

The cipher suites defined in this draft use short authentication tags for encryption, however it can easily support other ciphers with full authentication tag if the short ones are proved insecure.¶

7.4. Replay

The handling of replay is out of the scope of this document. However, senders MUST reject requests to encrypt multiple times with the same key and nonce, since several AEAD algorithms fail badly in such cases (see, e.g., Section 5.1.1 of [RFC5116]).¶

8.1. SFrame Cipher Suites

This registry lists identifiers for SFrame cipher suites, as defined in Section 4.5. The cipher suite field is two bytes wide, so the valid cipher suites are in the range 0x0000 to 0xFFFF.¶

Template:¶

• Value: The numeric value of the cipher suite¶
• Name: The name of the cipher suite¶
• Reference: The document where this wire format is defined¶

Initial contents:¶

9.1. Header Value Uniqueness

Applications MUST ensure that each (KID, CTR) combination is used for exactly one encryption operation. Typically this is done by assigning each sender a KID or set of KIDs, then having each sender use the CTR field as a monotonic counter, incrementing for each plaintext that is encrypted. Note that in addition to its simplicity, this scheme minimizes overhead by keeping CTR values as small as possible.¶

9.2. Key Management Framework

It is up to the application to provision SFrame with a mapping of KID values to base_key values and the resulting keys and salts. More importantly, the application specifies which KID values are used for which purposes (e.g., by which senders). An applications KID assignment strategy MUST be structured to assure the non-reuse properties discussed above.¶

It is also up to the application to define a rotation schedule for keys. For example, one application might have an ephemeral group for every call and keep rotating keys when end points join or leave the call, while another application could have a persistent group that can be used for multiple calls and simply derives ephemeral symmetric keys for a specific call.¶

It should be noted that KID values are not encrypted by SFrame, and are thus visible to any application-layer intermediaries that might handle an SFrame ciphertext. If there are application semantics included in KID values, then this information would be exposed to intermediaries. For example, in the scheme of Section 5.1, the number of ratchet steps per sender is exposed, and in the scheme of Section 5.2, the number of epochs and the MLS sender ID of the SFrame sender are exposed.¶

9.3. Anti-Replay

It is the responsibility of the application to handle anti-replay. Replay by network attackers is assumed to be prevented by network-layer facilities (e.g., TLS, SRTP). As mentioned in Section 7.4, senders MUST reject requests to encrypt multiple times with the same key and nonce.¶

It is not mandatory to implement anti-replay on the receiver side. Receivers MAY apply time or counter based anti-replay mitigations.¶

9.4. Metadata

The metadata input to SFrame operations is pure application-specified data. As such, it is up to the application to define what information should go in the metadata input and ensure that it is provided to the encryption and decryption functions at the appropriate points. A receiver SHOULD NOT use SFrame-authenticated metadata until after the SFrame decrypt function has authenticated it.¶

Note: The metadata input is a feature at risk, and needs more confirmation that it is useful and/or needed.¶

C.1. Assumptions

In the below calculations, we make conservative assumptions about SFrame overhead, so that the overhead amounts we compute here are likely to be an upper bound on those seen in practice.¶

In total, then, we assume that each SFrame encryption will add 22 bytes of overhead.¶

We consider two scenarios, applying SFrame per-frame and per-packet. In each scenario, we compute the SFrame overhead in absolute terms (Kbps) and as a percentage of the base bandwidth.¶

C.2. Audio

In audio streams, there is typically a one-to-one relationship between frames and packets, so the overhead is the same whether one uses SFrame at a per-packet or per-frame level.¶

The below table considers three scenarios, based on recommended configurations of the Opus codec [RFC6716]:¶

• Narrow-band speech: 120ms packets, 8Kbps¶
• Full-band speech: 20ms packets, 32Kbps¶
• Full-band stereo music: 10ms packets, 128Kbps¶

C.3. Video

Video frames can be larger than an MTU and thus are commonly split across multiple frames. Table 5 and Table 6 show the estimated overhead of encrypting a video stream, where SFrame is applied per-frame and per-packet, respectively. The choices of resolution, frames per second, and bandwidth are chosen to roughly reflect the capabilities of modern video codecs across a range from very low to very high quality.¶

In the per-frame case, the SFrame percentage overhead approaches zero as the quality of the video goes up, since bandwidth is driven more by picture size than frame rate. In the per-packet case, the SFrame percentage overhead approaches the ratio between the SFrame overhead per packet and the MTU (here 22 bytes of SFrame overhead divided by an assumed 1200-byte MTU, or about 1.8%).¶

C.4. Conferences

Real conferences usually involve several audio and video streams. The overhead of SFrame in such a conference is the aggregate of the overhead over all the individual streams. Thus, while SFrame incurs a large percentage overhead on an audio stream, if the conference also involves a video stream, then the audio overhead is likely negligible relative to the overall bandwidth of the conference.¶

For example, Table 7 shows the overhead estimates for a two person conference where one person is sending low-quality media and the other sending high-quality. (And we assume that SFrame is applied per-frame.) The video streams dominate the bandwidth at the SFU, so the total bandwidth overhead is only around 1%.¶

C.5. SFrame over RTP

SFrame is a generic encapsulation format, but many of the applications in which it is likely to be integrated are based on RTP. This section discusses how an integration between SFrame and RTP could be done, and some of the challenges that would need to be overcome.¶

As discussed in Section 4.1, there are two natural patterns for integrating SFrame into an application: applying SFrame per-frame or per-packet. In RTP-based applications, applying SFrame per-packet means that the payload of each RTP packet will be an SFrame ciphertext, starting with an SFrame Header, as shown in Figure 9. Applying SFrame per-frame means that different RTP payloads will have different formats: The first payload of a frame will contain the SFrame headers, and subsequent payloads will contain further chunks of the ciphertext, as shown in Figure 10.¶

In order for these media payloads to be properly interpreted by receivers, receivers will need to be configured to know which of the above schemes the sender has applied to a given sequence of RTP packets. SFrame does not provide a mechanism for distributing this configuration information. In applications that use SDP for negotiating RTP media streams [RFC4566], an appropriate extension to SDP could provide this function.¶

Applying SFrame per-frame also requires that packetization and depacketization be done in a generic manner that does not depend on the media content of the packets, since the content being packetized / depacketized will be opaque ciphertext (except for the SFrame header). In order for such a generic packetization scheme to work interoperably one would have to be defined, e.g., as proposed in [I-D.codec-agnostic-rtp-payload-format].¶

D.1. AES_CTR_128_HMAC_SHA256_4

CipherSuite:    0x01
Base Key:       101112131415161718191a1b1c1d1e1f
Key:            343d3290f5c0b936415bea9a43c6f5a2
Salt:           42d662fbad5cd81eb3aad79a
Plaintext:      46726f6d2068656176656e6c79206861
                726d6f6e79202f2f205468697320756e
                6976657273616c206672616d65206265
                67616e

KID:            0x7
CTR:            0x0
Header:         0700
Nonce:          42d662fbad5cd81eb3aad79a
Ciphertext:     0700c5095af9dbbbed6a952de114ea7b
                42768509f1ffc9749abb1e95bf4514d8
                d82a0eef4b5ecac16fa193977fa1aa1c
                9fa5c7e730b934669c

KID:            0x7
CTR:            0x1
Header:         0701
Nonce:          42d662fbad5cd81eb3aad79b
Ciphertext:     0701559e262525382885c6c93be8f61a
                9064db2dd1e1e96ab1dbd829ca4af4f4
                5f2b97a4889217a3f8a2159fb8201b7d
                71db01702b9caf8df6

KID:            0x7
CTR:            0x2
Header:         0702
Nonce:          42d662fbad5cd81eb3aad798
Ciphertext:     07020a8f21e052eaa09e50da0a909d15
                6cc55b9ef2f2abbcca765f7af3cfb1af
                234e3eac1dbc376631c83cf1ff1f8ab3
                39dbc41044742c668d

KID:            0xf
CTR:            0xaa
Header:         080faa
Nonce:          42d662fbad5cd81eb3aad730
Ciphertext:     080faa9c65aa5b167873f25827f17bc3
                4879a4aaa6b38dd9584472e1849d5da5
                1555f288d08f03166a5f26af01794006
                255c88b589861e2f8e3e

KID:            0x1ff
CTR:            0xaa
Header:         0901ffaa
Nonce:          42d662fbad5cd81eb3aad730
Ciphertext:     0901ffaa9c65aa5b167873f25827f17b
                c34879a4aaa6b38dd9584472e1849d5d
                a51555f288d08f03166a5f26af017940
                06255c88b58986ca1ead10

KID:            0x1ff
CTR:            0xaaaa
Header:         1901ffaaaa
Nonce:          42d662fbad5cd81eb3aa7d30
Ciphertext:     1901ffaaaa990cbeb4ae2e3a76be8bb9
                54b62591e791d0fa53c0553bc1d1e021
                d270b1a10688cd89195203b019789253
                73b04f9c08c3a4e563e2f6b9

KID:            0xffffffffffffff
CTR:            0xffffffffffffff
Header:         6effffffffffffffffffffffffffff
Nonce:          42d662fbada327e14c552865
Ciphertext:     6effffffffffffffffffffffffffff41
                2c43c8077c286f7df3dd9988d1bd033f
                1067493e09421e5bfc363e50a3c803b4
                da9239514cb924dbcb5f33e33112083e
                99108de2ecd6

D.2. AES_CTR_128_HMAC_SHA256_8

CipherSuite:    0x02
Base Key:       202122232425262728292a2b2c2d2e2f
Key:            3fce747d505e46ec9b92d9f58ee7a5d4
Salt:           77fbf5f1d82c73f6d2b353c9
Plaintext:      46726f6d2068656176656e6c79206861
                726d6f6e79202f2f205468697320756e
                6976657273616c206672616d65206265
                67616e

KID:            0x7
CTR:            0x0
Header:         0700
Nonce:          77fbf5f1d82c73f6d2b353c9
Ciphertext:     07009d89e5753e06edf3025f1ccd70b0
                95ebaf10c250e11da740f50f57b6ce86
                0d7321dfa49688a2cd6c6d9a71ae9d5c
                14ad0978efdd719a7f18c48f07

KID:            0x7
CTR:            0x1
Header:         0701
Nonce:          77fbf5f1d82c73f6d2b353c8
Ciphertext:     0701becd2e9d10e3eed586491b3e0ece
                dba89407ae2151787c5117b55707d6b8
                a0754f4dc937e30ebdf7cafbd3769d65
                85d7991b1a6bd31e8bddb1adec

KID:            0x7
CTR:            0x2
Header:         0702
Nonce:          77fbf5f1d82c73f6d2b353cb
Ciphertext:     070298508be6b16d034f15b504ced45a
                86d1bb43ed7cd3a62bf25557d1b082b0
                4e8e6ba6fe76160835dd8953e1be9640
                c988627ea447127ae4c103eabd

KID:            0xf
CTR:            0xaa
Header:         080faa
Nonce:          77fbf5f1d82c73f6d2b35363
Ciphertext:     080faae7eec4b0556ddfb8068998351c
                d670ce95f0ce9cd4c6dca2eeee73fb14
                d20a0d0fd487337ed43fa7f98dad0995
                b8b870325aa35a105af9b1004b22

KID:            0x1ff
CTR:            0xaa
Header:         0901ffaa
Nonce:          77fbf5f1d82c73f6d2b35363
Ciphertext:     0901ffaae7eec4b0556ddfb806899835
                1cd670ce95f0ce9cd4c6dca2eeee73fb
                14d20a0d0fd487337ed43fa7f98dad09
                95b8b870325aa3437cce05a6e67ee8

KID:            0x1ff
CTR:            0xaaaa
Header:         1901ffaaaa
Nonce:          77fbf5f1d82c73f6d2b3f963
Ciphertext:     1901ffaaaa8c1789aa0abcd6abc27006
                aae4df5cba4ba07f8113080e9726baac
                d16c18539974a6204a36b9dc3dcd36ed
                9ab48e590d95d4adfb4290f4cb1ba184

KID:            0xffffffffffffff
CTR:            0xffffffffffffff
Header:         6effffffffffffffffffffffffffff
Nonce:          77fbf5f1d8d38c092d4cac36
Ciphertext:     6effffffffffffffffffffffffffffa9
                bc6c7edde0fdfd13255a5b145c5ce84d
                b8f8960858eb998b8ea8f3e770160150
                813c5806441b64251bdd2be9e8cec138
                6b6f8e3b1982bcd16c84

D.3. AES_GCM_128_SHA256

CipherSuite:    0x03
Base Key:       303132333435363738393a3b3c3d3e3f
Key:            2ea2e8163ff56c0613e6fa9f20a213da
Salt:           a80478b3f6fba19983d540d5
Plaintext:      46726f6d2068656176656e6c79206861
                726d6f6e79202f2f205468697320756e
                6976657273616c206672616d65206265
                67616e

KID:            0x7
CTR:            0x0
Header:         0700
Nonce:          a80478b3f6fba19983d540d5
Ciphertext:     07000e426255e47ed70dd7d15d69d759
                bf459032ca15f5e8b2a91e7d348aa7c1
                86d403f620801c495b1717a35097411a
                a97cbb1406afd9f4e5215b46e4a39dc4
                0c27fd6bc7

KID:            0x7
CTR:            0x1
Header:         0701
Nonce:          a80478b3f6fba19983d540d4
Ciphertext:     070103bbafa34ada8a6b9f2066bc34a1
                959d87384c9f4b1ce34fed58e938bde1
                43393910b1aeb55b48d91d5b0db3ea67
                e3d0e02b84e4cf8ecf81f8386f86cda4
                8fcd754191

KID:            0x7
CTR:            0x2
Header:         0702
Nonce:          a80478b3f6fba19983d540d7
Ciphertext:     070258d58adebd8bf6f3cc0c1fcacf34
                ba4d7a763b2683fe302a57f1be7f2a27
                4bf81b2236995fec1203cadb146cd402
                e1c52d5e6aceaa5252822d25acd0ce4b
                a14e31fa24

KID:            0xf
CTR:            0xaa
Header:         080faa
Nonce:          a80478b3f6fba19983d5407f
Ciphertext:     080faad0b1743bf5248f90869c945636
                6d55724d16bbe08060875815565e90b1
                14f9ccbdba192422b33848a1ae1e3bd2
                66a001b2f5bb64c0f1216bba82ab24b1
                ebd677c2ca29

KID:            0x1ff
CTR:            0xaa
Header:         0901ffaa
Nonce:          a80478b3f6fba19983d5407f
Ciphertext:     0901ffaad0b1743bf5248f90869c9456
                366d55724d16bbe08060875815565e90
                b114f9ccbdba192422b33848a1ae1e3b
                d266a001b2f5bb8c718170432b6f922c
                1f0fb307514a0e

KID:            0x1ff
CTR:            0xaaaa
Header:         1901ffaaaa
Nonce:          a80478b3f6fba19983d5ea7f
Ciphertext:     1901ffaaaa9de65e21e4f1ca2247b879
                43c03c5cb7b182090e93d508dcfb76e0
                8174c6397356e682d2eaddabc0b3c101
                8d2c13c3570f61c185789dff3cb4469c
                f471ca71ceb025a5

KID:            0xffffffffffffff
CTR:            0xffffffffffffff
Header:         6effffffffffffffffffffffffffff
Nonce:          a80478b3f6045e667c2abf2a
Ciphertext:     6effffffffffffffffffffffffffff09
                981bdcdad80e380b6f74cf6afdbce946
                839bedadd57578bfcd809dbcea535546
                cc24660613d2761adea852155785011e
                633522450f95fd9f8ccc96fa3de9a247
                cfd3

D.4. AES_GCM_256_SHA512

CipherSuite:    0x04
Base Key:       404142434445464748494a4b4c4d4e4f
                505152535455565758595a5b5c5d5e5f
Key:            436774b0b5ae45633d96547f8f3cb06c
                8e6628eff2e4255b5c4d77e721aa3355
Salt:           31ed26f90a072e6aee646298
Plaintext:      46726f6d2068656176656e6c79206861
                726d6f6e79202f2f205468697320756e
                6976657273616c206672616d65206265
                67616e

KID:            0x7
CTR:            0x0
Header:         0700
Nonce:          31ed26f90a072e6aee646298
Ciphertext:     0700f3e297c1e95207710bd31ccc4ba3
                96fbef7b257440bde638ff0f3c891154
                0136df61b26220249d6c432c245ae8d5
                5ef45bfccf3afe18dd36d64d8e341653
                e1a0f10be2

KID:            0x7
CTR:            0x1
Header:         0701
Nonce:          31ed26f90a072e6aee646299
Ciphertext:     070193268b0bf030071bff443bb6b447
                1bdfb1cc81bc9625f4697b0336ff4665
                d15f152f02169448d8a967fb06359a87
                d2145398de044ee92acfcc27b7a98f38
                712b60c28c

KID:            0x7
CTR:            0x2
Header:         0702
Nonce:          31ed26f90a072e6aee64629a
Ciphertext:     0702649691ba27c4c01a41280fba4657
                c03fa7fe21c8f5c862e9094227c3ca3e
                c0d9468b1a2cb060ff0978f25a24e6b1
                06f5a6e10534b69d975605f31534caea
                88b33b455a

KID:            0xf
CTR:            0xaa
Header:         080faa
Nonce:          31ed26f90a072e6aee646232
Ciphertext:     080faa2858c10b5ddd231c1f26819490
                521678603a050448d563c503b1fd890d
                02ead01d754f074ecb6f32da9b2f3859
                f380b4f47d4ed539d6103e61580a82c0
                14b28eb48b4a

KID:            0x1ff
CTR:            0xaa
Header:         0901ffaa
Nonce:          31ed26f90a072e6aee646232
Ciphertext:     0901ffaa2858c10b5ddd231c1f268194
                90521678603a050448d563c503b1fd89
                0d02ead01d754f074ecb6f32da9b2f38
                59f380b4f47d4e32c565b3b3fa20fc7e
                cff21a1cee3eec

KID:            0x1ff
CTR:            0xaaaa
Header:         1901ffaaaa
Nonce:          31ed26f90a072e6aee64c832
Ciphertext:     1901ffaaaad9bc6a258a07d210a814d5
                45eca70321c0e87498ada6e5c708b7ea
                d162ffcf4fbaba1eb82650590a87122b
                4d95fe36bd88b278994922fe5c09f14c
                728521333297f84f

KID:            0xffffffffffffff
CTR:            0xffffffffffffff
Header:         6effffffffffffffffffffffffffff
Nonce:          31ed26f90af8d195119b9d67
Ciphertext:     6effffffffffffffffffffffffffffaf
                480d4779ce0c02b5137ee6a61e026c04
                ac999cb0c97319feceeb258d58df23bc
                e14979e5c67a431777b34498062e72f9
                39ca4acb471bad80259bb44f78a15248
                7e67