jiebi/TextFlow huggingface dataset:
Original text:
A signature algorithm <del> The HPKE parameters are used to instantiate HPKE I-D.irtf-cfrg-hpke for the purpose of public-key encryption.  The "DeriveKeyPair" function associated to the KEM for the ciphersuite maps octet strings to HPKE key pairs. </del>  Ciphersuites are represented with the CipherSuite type.  HPKE public keys are opaque values in a format defined by the underlying protocol

Reviewer comments:
cc NAME
NAME is the build expected to fail?
No, but the problem seem unrelated to your change, so we are all good.
Looks like it was a transient failure. Re-running resulted in success.
NAME points out that the HPKE version is not pinned. This is probably needed for interop. Version -07 should come sometime this week, so that seems like a perfectly fine version to use. I can send a PR when that version is cut.
Fixed by

Revised text:
A signature algorithm  <ins> MLS uses draft-07 of HPKE I-D.irtf-cfrg-hpke for public-key encryption.  The "DeriveKeyPair" function associated to the KEM for the ciphersuite maps octet strings to HPKE key pairs. </ins> Ciphersuites are represented with the CipherSuite type.  HPKE public keys are opaque values in a format defined by the underlying protocol
Original text:
Name: The name of the ciphersuite <del> Recommended: Whether support for this extension is recommended by the IETF MLS WG.  Valid values are "Y" and "N".  The "Recommended" column is assigned a value of "N" unless explicitly requested, and adding a value with a "Recommended" value of "Y" requires Standards Action RFC8126.  IESG Approval is REQUIRED for a Y->N transition. </del>  Reference: The document where this ciphersuite is defined

Reviewer comments:
I noticed a bunch of typos in the "IANA Considerations" section: the "ciphersuites" and "credentials" were probably copy-pasted from the "extension" one, and some parts were not changed correctly. This PR fixes these typos.
Discussed 20210526 Interim: editorial will be taken up by editors.
Thanks!

Revised text:
Name: The name of the ciphersuite  <ins> Recommended: Whether support for this ciphersuite is recommended by the IETF MLS WG.  Valid values are "Y" and "N".  The "Recommended" column is assigned a value of "N" unless explicitly requested, and adding a value with a "Recommended" value of "Y" requires Standards Action RFC8126.  IESG Approval is REQUIRED for a Y->N transition. </ins> Reference: The document where this ciphersuite is defined
Original text:
16.3. This registry lists identifiers for types of credentials that can be <del> used for authentication in the MLS protocol.  The extension type field is two bytes wide, so valid extension type values are in the </del>  range 0x0000 to 0xffff. Template:

Reviewer comments:
I noticed a bunch of typos in the "IANA Considerations" section: the "ciphersuites" and "credentials" were probably copy-pasted from the "extension" one, and some parts were not changed correctly. This PR fixes these typos.
Discussed 20210526 Interim: editorial will be taken up by editors.
Thanks!

Revised text:
16.3. This registry lists identifiers for types of credentials that can be  <ins> used for authentication in the MLS protocol.  The credential type field is two bytes wide, so valid credential type values are in the </ins> range 0x0000 to 0xffff. Template:
Original text:
Name: The name of the credential type <del> Recommended: Whether support for this extension is recommended by </del>  the IETF MLS WG.  Valid values are "Y" and "N".  The "Recommended" column is assigned a value of "N" unless explicitly requested, and adding a value with a "Recommended" value of "Y" requires Standards Action RFC8126.  IESG Approval is REQUIRED for a Y->N transition. <del> Reference: The document where this extension is defined </del>  Initial contents:

Reviewer comments:
I noticed a bunch of typos in the "IANA Considerations" section: the "ciphersuites" and "credentials" were probably copy-pasted from the "extension" one, and some parts were not changed correctly. This PR fixes these typos.
Discussed 20210526 Interim: editorial will be taken up by editors.
Thanks!

Revised text:
Name: The name of the credential type  <ins> Recommended: Whether support for this credential is recommended by </ins> the IETF MLS WG.  Valid values are "Y" and "N".  The "Recommended" column is assigned a value of "N" unless explicitly requested, and adding a value with a "Recommended" value of "Y" requires Standards Action RFC8126.  IESG Approval is REQUIRED for a Y->N transition.  <ins> Reference: The document where this credential is defined </ins> Initial contents:
Original text:
Each leaf is given an _index_ (or _leaf index_), starting at "0" from the left to "n-1" at the right.  There are multiple ways that an implementation might represent a ratchet tree in memory.  For example, left-balanced binary trees can be represented as an array of nodes, with node relationships computed

Reviewer comments:
The definition of blank node needs to move ahead into ## Ratchet Tree Terminology as it is used in the section immediately following (## Views of a Ratchet Tree).

Revised text:
Each leaf is given an _index_ (or _leaf index_), starting at "0" from the left to "n-1" at the right. <ins> Finally, a node in the tree may also be _blank_, indicating that no value is present at that node (i.e. no keying material).  This is often the case when a leaf was recently removed from the tree. </ins> There are multiple ways that an implementation might represent a ratchet tree in memory.  For example, left-balanced binary trees can be represented as an array of nodes, with node relationships computed
Original text:
The conditions under which each of these values must or must not be present are laid out in views. <del> A node in the tree may also be _blank_, indicating that no value is present at that node.  The _resolution_ of a node is an ordered list of non-blank nodes that collectively cover all non-blank descendants of the node.  The resolution of a non-blank node with no unmerged leaves is just the node itself.  More generally, the resolution of a node is effectively a depth-first, left-first enumeration of the nearest non-blank nodes below the node: </del>  The resolution of a non-blank node comprises the node itself, followed by its list of unmerged leaves, if any

Reviewer comments:
The definition of blank node needs to move ahead into ## Ratchet Tree Terminology as it is used in the section immediately following (## Views of a Ratchet Tree).

Revised text:
The conditions under which each of these values must or must not be present are laid out in views.  <ins> The _resolution_ of a node is an ordered list of non-blank nodes that collectively cover all non-blank descendants of the node.  The resolution of a non-blank node with no unmerged leaves is just the node itself.  More generally, the resolution of a node is effectively a depth-first, left-first enumeration of the nearest non-blank nodes below the node: </ins> The resolution of a non-blank node comprises the node itself, followed by its list of unmerged leaves, if any
Original text:
committer's contribution to the group and provides PCS with regard to the committer. <del> A "partial" Commit that references Add, PreSharedKey, or ReInit proposals but where the path is empty.  Such a commit doesn't provide PCS with regard to the committer. </del>  A "full" Commit that references proposals of any type, which provides FS with regard to any removed members and PCS for the

Reviewer comments:
This PR introduces a notion of a proposal type being "path safe", in the sense that it is safe for the path to be omitted. (Better phrasing welcome!) The field is required default, and allowed to be omitted only if all the proposals in the Commit are path-safe.
Thanks for taking care of this fix! One suggestion: Instead of having a global list of which types are path safe and which ones aren't, we could make it a property of the proposal. Maybe something like this: Regarding the name, the only thing I can think of is that we could invert the property and call it : In fact, I think I'd be slightly in favor of the latter proposal.
Discussion on virtual interim: OK to keep using type TODO(NAME "path safe" -> "path required" Otherwise clear to merge
The authoritative definition (in Section ) of when to include a is not the same as the summary below. For example, if an implementation adds a custom proposal type, according to the summary, a path is required, whereas according to the definition above it, no path is required. Ultimately, it depends on the nature of the proposal and the desired security guarantees if a path is required. However, I think the safer option is to require a path by default and maybe leave it to the definition of the respective custom proposal to explicitly specify if a path is not required.

Revised text:
committer's contribution to the group and provides PCS with regard to the committer.  <ins> A "partial" Commit that references proposals that do not require a path, and where the path is empty.  Such a commit doesn't provide PCS with regard to the committer. </ins> A "full" Commit that references proposals of any type, which provides FS with regard to any removed members and PCS for the
Original text:
The following structure is used to fully describe the data transmitted in plaintexts or ciphertexts.  7.1. MLSMessageContent is authenticated using the MLSMessageAuth

Reviewer comments:
I drew this to help explain the relevant patch in MLSpp to someone, and thought it might be helpful to other folks.
Excellent! This is a very nice addition to explain the design introduced .

Revised text:
The following structure is used to fully describe the data transmitted in plaintexts or ciphertexts. <ins> The following figure illustrates how the various structures described in this section relate to each other, and the high-level operations used to produce and consume them: </ins> 7.1. MLSMessageContent is authenticated using the MLSMessageAuth
Original text:
cryptographic state of the group, this section defines a scheme for generating a hash value (called the "tree hash") that represents the contents of the group's ratchet tree and the members' leaf nodes. <del> The tree hash of a tree is the tree hash of its root node, which we define recursively, starting with the leaves. The tree hash of a leaf node is the hash of leaf's "LeafNodeHashInput" object which might include a "LeafNode" object depending on whether or not it is blank. Now the tree hash of any non-leaf node is recursively defined to be the hash of its "ParentNodeHashInput".  This includes an optional "ParentNode" object depending on whether the node is blank or not. The "left_hash" and "right_hash" fields hold the tree hashes of the node's left and right children, respectively. </del>  8.8.

Reviewer comments:
I'm not sure if this is actually necessary, but there usually seem to be issues in Merkle trees when the leaves are not explicitly distinct from the parents.
I would find it nicer to describe things with a like in other parts of the protocol: It is equivalent to your modification. Stating things that way ensures there is no ambiguity: TreeHashInput is parseable, which is I think the property you want to ensure with this PR.
Use enum instead and then ready for merge.
Interim 2022-05-26: Nicer with an NAME to update to , then merge
When computing the tree hash, should there be an indicator bit for whether the value being hashed represents a leaf or parent node?
This doesn't seem like a terrible idea. You could either add a field to LeafNodeHashInput and ParentNodeHashInput, or define an enum and do the same, or make a . For example:

Revised text:
cryptographic state of the group, this section defines a scheme for generating a hash value (called the "tree hash") that represents the contents of the group's ratchet tree and the members' leaf nodes.  <ins> The tree hash of an individual node is the hash of the node's "TreeHashInput" object, which may contain either a "LeafNodeHashInput" or a "ParentNodeHashInput" depending on the type of node.  "LeafNodeHashInput" objects contain the "leaf_index" and the "LeafNode" (if any).  "ParentNodeHashInput" objects contain the "ParentNode" (if any) and the tree hash of the node's left and right children. The tree hash of an entire tree corresponds to the tree hash of the root node, which is computed recursively by starting at the leaf nodes and building up. </ins> 8.8.
Original text:
input to the key schedule, the Commit and GroupSecrets objects MUST indicate the same set of PSKs, in the same order.  On receiving a Commit with a "PreSharedKey" proposal or a GroupSecrets object with the "psks" field set, the receiving Client includes them in the key schedule in the order listed in the Commit,

Reviewer comments:
Also covers the PSK part of
Interim 2022-05-26: Ready to go once merge conflicts are resolved.
The collection of structs could be less chatty. Suggest PreSharedKeys is only used once, can be inlined in GroupSecrets Use GroupContext for the internals of GroupInfo
Note: was fixed in In , we did: So only the following remain: Use GroupContext for the internals of GroupInfo
currently described at time of use. In the "Pre-Shared Keys" section, we should just specify that it must always be a fresh value of length The ReInit provisions require , but those for branching do not. Presumably these should be the same? Currently, the processing rules for PreSharedKey proposal says “MUST be external”. This seems overly restrictive; for example, it rules out the scenario in Figure 8. Suggest “MUST NOT be branch/reinit” instead.

Revised text:
input to the key schedule, the Commit and GroupSecrets objects MUST indicate the same set of PSKs, in the same order. <ins> Each time a client injects a PSK into a group, the "psk_nonce" of its PreSharedKeyID MUST be set to a fresh random value of length "KDF.Nh", where "KDF" is the KDF for the ciphersuite of the group into which the PSK is being injected.  This ensures that even when a PSK is used multiple times, the value used as an input into the key schedule is different each time. </ins> On receiving a Commit with a "PreSharedKey" proposal or a GroupSecrets object with the "psks" field set, the receiving Client includes them in the key schedule in the order listed in the Commit,
Original text:
Welcome message MUST be the same as the corresponding fields in the ReInit proposal. <del> The "epoch" in the Welcome message MUST be 1 </del> The Welcome MUST specify a PreSharedKey of type "resumption" with usage "reinit".  The "group_id" must match the old group, and the "epoch" must indicate the epoch after the Commit covering the ReInit. <del> The "psk_nonce" included in the "PreSharedKeyID" of the resumption PSK MUST be a randomly sampled nonce of length "KDF.Nh", for the KDF defined by the new group's ciphersuite. </del> Note that these three steps may be done by the same group member or different members.  For example, if a group member sends a commit with an inline ReInit proposal (steps 1 and 2), but then goes

Reviewer comments:
Also covers the PSK part of
Interim 2022-05-26: Ready to go once merge conflicts are resolved.
The collection of structs could be less chatty. Suggest PreSharedKeys is only used once, can be inlined in GroupSecrets Use GroupContext for the internals of GroupInfo
Note: was fixed in In , we did: So only the following remain: Use GroupContext for the internals of GroupInfo
currently described at time of use. In the "Pre-Shared Keys" section, we should just specify that it must always be a fresh value of length The ReInit provisions require , but those for branching do not. Presumably these should be the same? Currently, the processing rules for PreSharedKey proposal says “MUST be external”. This seems overly restrictive; for example, it rules out the scenario in Figure 8. Suggest “MUST NOT be branch/reinit” instead.

Revised text:
Welcome message MUST be the same as the corresponding fields in the ReInit proposal.  The Welcome MUST specify a PreSharedKey of type "resumption" with usage "reinit".  The "group_id" must match the old group, and the "epoch" must indicate the epoch after the Commit covering the ReInit.  Note that these three steps may be done by the same group member or different members.  For example, if a group member sends a commit with an inline ReInit proposal (steps 1 and 2), but then goes
Original text:
The "version" and "ciphersuite" values in the Welcome MUST be the same as those used by the old group.  Each LeafNode in a new subgroup MUST match some LeafNode in the original group.  In this context, a pair of LeafNodes is said to "match" if the identifiers presented by their respective credentials are considered equivalent by the application. <del> In addition, to avoid key re-use, the "psk_nonce" included in the "PreSharedKeyID" object MUST be a randomly sampled nonce of length "KDF.Nh". </del> Resumption PSKs with usage "branch" MUST NOT be used in other contexts.  A PreSharedKey proposal with type "resumption" and usage "branch" MUST be considered invalid.

Reviewer comments:
Also covers the PSK part of
Interim 2022-05-26: Ready to go once merge conflicts are resolved.
The collection of structs could be less chatty. Suggest PreSharedKeys is only used once, can be inlined in GroupSecrets Use GroupContext for the internals of GroupInfo
Note: was fixed in In , we did: So only the following remain: Use GroupContext for the internals of GroupInfo
currently described at time of use. In the "Pre-Shared Keys" section, we should just specify that it must always be a fresh value of length The ReInit provisions require , but those for branching do not. Presumably these should be the same? Currently, the processing rules for PreSharedKey proposal says “MUST be external”. This seems overly restrictive; for example, it rules out the scenario in Figure 8. Suggest “MUST NOT be branch/reinit” instead.

Revised text:
The "version" and "ciphersuite" values in the Welcome MUST be the same as those used by the old group. <ins> The "epoch" in the Welcome message MUST be 1. </ins> Each LeafNode in a new subgroup MUST match some LeafNode in the original group.  In this context, a pair of LeafNodes is said to "match" if the identifiers presented by their respective credentials are considered equivalent by the application.  Resumption PSKs with usage "branch" MUST NOT be used in other contexts.  A PreSharedKey proposal with type "resumption" and usage "branch" MUST be considered invalid.
Original text:
A PreSharedKey proposal is invalid if any of the following is true: The "psktype" in the PreSharedKeyID struct is not set to <del> "external". </del>  The "psk_nonce" is not of length "KDF.Nh".

Reviewer comments:
Also covers the PSK part of
Interim 2022-05-26: Ready to go once merge conflicts are resolved.
The collection of structs could be less chatty. Suggest PreSharedKeys is only used once, can be inlined in GroupSecrets Use GroupContext for the internals of GroupInfo
Note: was fixed in In , we did: So only the following remain: Use GroupContext for the internals of GroupInfo
currently described at time of use. In the "Pre-Shared Keys" section, we should just specify that it must always be a fresh value of length The ReInit provisions require , but those for branching do not. Presumably these should be the same? Currently, the processing rules for PreSharedKey proposal says “MUST be external”. This seems overly restrictive; for example, it rules out the scenario in Figure 8. Suggest “MUST NOT be branch/reinit” instead.

Revised text:
A PreSharedKey proposal is invalid if any of the following is true: The "psktype" in the PreSharedKeyID struct is not set to  <ins> "resumption" and the "usage" is "reinit" or "branch". </ins> The "psk_nonce" is not of length "KDF.Nh".
Original text:
A GroupContextExtensions proposal is used to update the list of extensions in the GroupContext for the group. <del> "struct { Extension extensions<V>; } GroupContextExtensions; " </del> A GroupContextExtensions proposal is invalid if it includes a "required_capabilities" extension and some members of the group do not support some of the required capabilities (including those added

Reviewer comments:
The enum was missing the limit. The wasn't using a TLS environment.
NAME shouldn't ResumptionPSKUsage include (255)? enum { reserved(0), application(1), reinit(2), branch(3), (255) } ResumptionPSKUsage;
Fixed in
Seems reasonable to me.

Revised text:
A GroupContextExtensions proposal is used to update the list of extensions in the GroupContext for the group.  A GroupContextExtensions proposal is invalid if it includes a "required_capabilities" extension and some members of the group do not support some of the required capabilities (including those added
Original text:
A signing key pair used to authenticate the sender of a message.  A PublicMessage or PrivateMessage carrying an MLS Proposal or Commit object, as opposed to application data.

Reviewer comments:
URL This definition of a handshake message is being defined in terms of a Proposal or Commit object, neither of which are defined in this session. Furthermore, PublicMessage or PrivateMessage aren’t defined either as this point in the text. To improve clarity, consider defining these key terms. The use of "respectively" in the text is suggesting that PrivateMessages don’t have integrity protection which is not accurate. (see the Cryptographic Dependencies section of the HPKE specification for more information). Is this Section 4 of RFC9180?  If so, why not say that? What would be the circumstance where the application_id extension would be treated with equal standing as something from the AS?  Why can’t this be a "MUST"? Unsaid is what to do if the proposal list is not valid.  Please clarify. Is this normative behavior required, or could it be left up to application?  The mixing of updates/removes on the same node and the SHOULD guidance already means that this "recovery from an invalid node" may not be consistent across clients/DS-es. Same observation on recovering from ReInit with any other proposals. Is there any additional retry mechanism?  Let’s say the sender of the proposal doesn’t see it reflect in the epoch after it sent proposal.  And then not in the next epoch.  Does it try resending indefinitely? This setup seems a little simplistic. If the application data is encrypted to begin with, how does the adversary know the question being posed by Alice?

Revised text:
A signing key pair used to authenticate the sender of a message. <ins> A message that proposes a change to the group, e.g., adding or removing a member. A message that implements the changes to the group proposed in a set of Proposals. An MLS protocol message that is signed by its sender and authenticated as coming from a member of the group in a particular epoch, but not encrypted. An MLS protocol message that is both signed by its sender, authenticated as coming from a member of the group in a particular epoch, and encrypted so that it is confidential to the members of the group in that epoch. </ins> A PublicMessage or PrivateMessage carrying an MLS Proposal or Commit object, as opposed to application data.