RFC 8732
Generic Security Service Application Program Interface (GSS-API) Key Exchange with SHA-2
Generic Security Service Application Program Interface (GSS-API) Key Exchange with SHA-2 🦋
okay bestie, let's get into this one. It's RFC 8732, written by S. Sorce and H. Kario from Red Hat, Inc. It's on the Standards Track, dated February 2020, with ISSN 2070-1721 and the IETF (Internet Engineering Task Force) behind it. It updates RFC 4462 🎀 It's giving official protocol glow-up energy ✨
Abstract ✨
okay so the vibe here is that this doc adds to and amends RFC 4462 🌸 It brings in a brand new key exchange method that uses SHA-2 for integrity and also deprecates the weak Diffie-Hellman (DH) groups 💅 The whole point is to glow up the crypto primitives that Generic Security Service (GSS) key exchanges use. Main character modernization, literally 👑
Status of This Memo
so this is an Internet Standards Track document 💖
it's a product of the Internet Engineering Task Force (IETF), and it totally represents what the IETF community agreed on 🫶 It went through public review and got the green light from the Internet Engineering Steering Group (IESG) ✅ If you want more on Internet Standards, check out Section 2 of RFC 7841 🧚
for the current status, any errata, and how to send feedback, head to https://www.rfc-editor.org/info/rfc8732 🦋
Copyright Notice
📜 Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved.
this doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as they stand on the day it was published 🌈 Please read these carefully, because they spell out your rights and restrictions for this document, no cap 💀 Code Components pulled out of this document need to include the Simplified BSD License text, as Section 4.e of the Trust Legal Provisions describes, and they come with no warranty, same as the Simplified BSD License says 🎀
Table of Contents 🌸
1. Introduction
2. Rationale
3. Document Conventions
4. New Diffie-Hellman Key Exchange Methods
5. New Elliptic Curve Diffie-Hellman Key Exchange Methods
5.1. Generic GSS-API Key Exchange with ECDH
5.2. ECDH Key Exchange Methods
6. Deprecated Algorithms
7. IANA Considerations
8. Security Considerations
8.1. New Finite Field DH Mechanisms
8.2. New Elliptic Curve DH Mechanisms
8.3. GSS-API Delegation
9. References
9.1. Normative References
9.2. Informative References
Authors' Addresses1. Introduction ✨
okay so Secure Shell (SSH) Generic Security Service Application Program Interface (GSS-API) methods, defined in [RFC4462], let you use GSS-API [RFC2743] for authentication and key exchange in SSH 🔐 [RFC4462] lays out three exchange methods, and they're all built on DH groups and SHA-1 🙈 This document updates [RFC4462] with new methods meant for environments that want to use the SHA-2 cryptographic hash functions 💜
2. Rationale 💅
so here's the tea. SHA-1 has security concerns [RFC6194], and so do modular exponentiation (MODP) groups with less than 2048 bits [NIST-SP-800-131Ar2] 💀 That's why we're proposing hashes based on SHA-2 [RFC6234], paired with DH group14, group15, group16, group17, and group18 [RFC3526] 🍓
we're also adding key exchange based on Elliptic Curve Diffie-Hellman using the NIST P-256, P-384, and P-521 curves [SEC2v2], plus the X25519 and X448 curves [RFC7748] ✨ Following what [RFC8268] does, only SHA-256 and SHA-512 hashes get used for DH groups 🫶 And for the NIST curves, we're copying the same curve-to-hashing pairing that [RFC5656] uses, just for consistency 🦋
3. Document Conventions 🎀
the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be read as BCP 14 [RFC2119] [RFC8174] describes, but only when they show up in all capitals, exactly like that 🌈 Lowercase versions don't count, bestie 🙈
4. New Diffie-Hellman Key Exchange Methods 🌸
this doc uses the same naming convention that [RFC4462] set up, so families of methods can cover any GSS-API mechanism paired with a specific Diffie-Hellman group and SHA-2 hash combo 💖
+--------------------------+--------------------------------+
| Key Exchange Method Name | Implementation Recommendations |
+==========================+================================+
| gss-group14-sha256-* | SHOULD/RECOMMENDED |
+--------------------------+--------------------------------+
| gss-group15-sha512-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+
| gss-group16-sha512-* | SHOULD/RECOMMENDED |
+--------------------------+--------------------------------+
| gss-group17-sha512-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+
| gss-group18-sha512-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+Table 1: New Key Exchange Algorithms
each key exchange method prefix gets registered by this document 📝 The IESG is the change controller for all of these key exchange methods, but that does NOT mean the IESG controls the matching GSS-API mechanism 🧚
each method in any family (see Table 2) describes GSS-API-authenticated Diffie-Hellman key exchanges, the way Section 2.1 of [RFC4462] lays them out 🦋 A method name is made by sticking the family name prefix onto the base64 encoding of the MD5 hash [RFC1321] of the ASN.1 DER encoding [ISO-IEC-8825-1] of the GSS-API mechanism's OID 🔥 Base64 encoding is covered in Section 4 of [RFC4648] 💫
+---------------------+---------------+----------+--------------+
| Family Name Prefix | Hash Function | Group | Reference |
+=====================+===============+==========+==============+
| gss-group14-sha256- | SHA-256 | 2048-bit | Section 3 of |
| | | MODP | [RFC3526] |
+---------------------+---------------+----------+--------------+
| gss-group15-sha512- | SHA-512 | 3072-bit | Section 4 of |
| | | MODP | [RFC3526] |
+---------------------+---------------+----------+--------------+
| gss-group16-sha512- | SHA-512 | 4096-bit | Section 5 of |
| | | MODP | [RFC3526] |
+---------------------+---------------+----------+--------------+
| gss-group17-sha512- | SHA-512 | 6144-bit | Section 6 of |
| | | MODP | [RFC3526] |
+---------------------+---------------+----------+--------------+
| gss-group18-sha512- | SHA-512 | 8192-bit | Section 7 of |
| | | MODP | [RFC3526] |
+---------------------+---------------+----------+--------------+Table 2: Family Method References
5. New Elliptic Curve Diffie-Hellman Key Exchange Methods 🧚
so [RFC5656] brought in new SSH key exchange algorithms based on elliptic curve cryptography 🌈 We borrow a lot of Section 4 of [RFC5656] to define GSS-API-authenticated Elliptic Curve Diffie-Hellman (ECDH) key exchanges, which is so efficient, honestly 💜
we also use the curves defined in [RFC8731] 🎀 They complement the three classic NIST-defined curves that [RFC5656] requires, so we get a whole squad of curves now 👑✨
5.1. Generic GSS-API Key Exchange with ECDH ✨
okay bestie, this section is basically a mashup 💖 It reuses a lot of the scheme from Section 2.1 of [RFC4462] and blends it with the scheme from Section 4 of [RFC5656]. The tea is that all the checks and verification steps from Section 4 of [RFC5656] apply here too, no exceptions 💅
The key-agreement schemes "ECDHE-Curve25519" and "ECDHE-Curve448" do the Diffie-Hellman protocol using the functions X25519 and X448 🌈 Implementations MUST compute these functions using the algorithms described in [RFC7748]. When they do, implementations MUST check whether the computed Diffie-Hellman shared secret is the all-zero value and abort if so, as described in Section 6 of [RFC7748] 🚨 Alternative implementations of these functions SHOULD abort when either the client or the server input forces the shared secret to one of a small set of values, as described in Sections 6 and 7 of [RFC7748] 🔍
This section defers to [RFC7546] as the source of information on GSS-API context establishment operations, with Section 3 being the most relevant 📚 All security considerations described in [RFC7546] apply here, too 🔒
The parties each generate an ephemeral key pair, according to Section 3.2.1 of [SEC1v2] 🗝️ Keys are verified upon receipt by the parties according to Section 3.2.3.1 of [SEC1v2] ✨
For NIST curves, the keys use the uncompressed point representation and MUST be converted using the algorithm in Section 2.3.4 of [SEC1v2]. If the conversion fails or the point is transmitted using the compressed representation, the key exchange MUST fail 🙅
A GSS context is established according to Section 4 of [RFC5656] 🎀 The client kicks it off with GSS_Init_sec_context(), and the server answers with GSS_Accept_sec_context(). For the negotiation, the client MUST set mutual_req_flag and integ_req_flag to "true" (no skipping, periodt 💅). deleg_req_flag MAY be set to "true" to request access delegation, if requested by the user 🔑 Since the key exchange process authenticates only the host, the setting of anon_req_flag is immaterial to this process 🙈
If the client does not support the "gssapi-keyex" user authentication method described in Section 4 of [RFC4462], or does not intend to use that method in conjunction with the GSS-API context established during key exchange, then anon_req_flag SHOULD be set to "true". Otherwise, this flag MAY be set to "true" if the client wishes to hide its identity 🕵️ This key exchange process will exchange only a single message token once the context has been established, so replay_det_req_flag and sequence_req_flag SHOULD be set to "false" 💜
The client MUST include its public key with the first message it sends to the server during this process. If the server receives more than one key or none at all, the key exchange MUST fail 🫶
During GSS context establishment, multiple tokens may be exchanged by the client and the server 🔁 When the GSS context is established (major_status is GSS_S_COMPLETE), the parties check that mutual_state and integ_avail are both "true". If not, the key exchange MUST fail 🧐
Once a party receives the peer's public key, it proceeds to compute a shared secret K 🧮 For NIST curves, the computation is done according to Section 3.3.1 of [SEC1v2], and the resulting value z is converted to the octet string K using the conversion defined in Section 2.3.5 of [SEC1v2]. For curve25519 and curve448, the algorithms in Section 6 of [RFC7748] are used instead ✨
To verify the integrity of the handshake, peers use the hash function defined by the selected key exchange method to calculate H:
H = hash(V_C || V_S || I_C || I_S || K_S || Q_C || Q_S || K).The server uses the GSS_GetMIC() call with H as the payload to generate a Message Integrity Code (MIC). The GSS_VerifyMIC() call is used by the client to verify the MIC 🔐
If any GSS_Init_sec_context() or GSS_Accept_sec_context() returns a major_status other than GSS_S_COMPLETE or GSS_S_CONTINUE_NEEDED, or any other GSS-API call returns a major_status other than GSS_S_COMPLETE, the key exchange MUST fail. The same recommendations expressed in Section 2.1 of [RFC4462] are followed with regard to error reporting 🚨
Here's the overview of the key exchange process 👀
Client Server
------ ------
Generates ephemeral key pair.
Calls GSS_Init_sec_context().
SSH_MSG_KEXGSS_INIT --------------->
Verifies received key.
(Optional) <------------- SSH_MSG_KEXGSS_HOSTKEY
(Loop)
| Calls GSS_Accept_sec_context().
| <------------ SSH_MSG_KEXGSS_CONTINUE
| Calls GSS_Init_sec_context().
| SSH_MSG_KEXGSS_CONTINUE ------------>
Calls GSS_Accept_sec_context().
Generates ephemeral key pair.
Computes shared secret.
Computes hash H.
Calls GSS_GetMIC( H ) = MIC.
<------------ SSH_MSG_KEXGSS_COMPLETE
Verifies received key.
Computes shared secret.
Computes hash H.
Calls GSS_VerifyMIC( MIC, H ).This is implemented with the following messages 🧩
The client sends:
byte SSH_MSG_KEXGSS_INIT
string output_token (from GSS_Init_sec_context())
string Q_C, client's ephemeral public key octet stringThe server may respond with:
byte SSH_MSG_KEXGSS_HOSTKEY
string server public host key and certificates (K_S)The server sends:
byte SSH_MSG_KEXGSS_CONTINUE
string output_token (from GSS_Accept_sec_context())Each time the client receives the message described above, it makes another call to GSS_Init_sec_context() 🔄
The client sends:
byte SSH_MSG_KEXGSS_CONTINUE
string output_token (from GSS_Init_sec_context())As the final message, the server sends the following if an output_token is produced 🏁
byte SSH_MSG_KEXGSS_COMPLETE
string Q_S, server's ephemeral public key octet string
string mic_token (MIC of H)
boolean TRUE
string output_token (from GSS_Accept_sec_context())If no output_token is produced, the server sends:
byte SSH_MSG_KEXGSS_COMPLETE
string Q_S, server's ephemeral public key octet string
string mic_token (MIC of H)
boolean FALSEThe hash H is computed as the HASH hash of the concatenation of the following 🧺
string V_C, the client's version string (CR, NL excluded)
string V_S, server's version string (CR, NL excluded)
string I_C, payload of the client's SSH_MSG_KEXINIT
string I_S, payload of the server's SSH_MSG_KEXINIT
string K_S, server's public host key
string Q_C, client's ephemeral public key octet string
string Q_S, server's ephemeral public key octet string
mpint K, shared secretThis value is called the "exchange hash", and it is used to authenticate the key exchange 🦋 The exchange hash SHOULD be kept secret. If no SSH_MSG_KEXGSS_HOSTKEY message has been sent by the server or received by the client, then the empty string is used in place of K_S when computing the exchange hash 🌸
Since this key exchange method does not require the host key to be used for any encryption operations, the SSH_MSG_KEXGSS_HOSTKEY message is OPTIONAL. If the "null" host key algorithm described in Section 5 of [RFC4462] is used, this message MUST NOT be sent 🙅
If the client receives an SSH_MSG_KEXGSS_CONTINUE message after a call to GSS_Init_sec_context() has returned a major_status code of GSS_S_COMPLETE, a protocol error has occurred, and the key exchange MUST fail 💀
If the client receives an SSH_MSG_KEXGSS_COMPLETE message and a call to GSS_Init_sec_context() does not result in a major_status code of GSS_S_COMPLETE, a protocol error has occurred, and the key exchange MUST fail 😭
5.2. ECDH Key Exchange Methods ✨
Okay bestie, here's the ECDH lineup 💖 Each method gets its own recommendation, and I'm keeping every single one exactly as written:
+--------------------------+--------------------------------+
| Key Exchange Method Name | Implementation Recommendations |
+==========================+================================+
| gss-nistp256-sha256-* | SHOULD/RECOMMENDED |
+--------------------------+--------------------------------+
| gss-nistp384-sha384-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+
| gss-nistp521-sha512-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+
| gss-curve25519-sha256-* | SHOULD/RECOMMENDED |
+--------------------------+--------------------------------+
| gss-curve448-sha512-* | MAY/OPTIONAL |
+--------------------------+--------------------------------+
Table 3: New Key Exchange MethodsEach key exchange method prefix is registered by this document. The IESG is the change controller of all these key exchange methods 🎀 but this does NOT imply that the IESG is considered to be in control of the corresponding GSS-API mechanism. Big difference, so don't mix them up 🙈
Each method in any family of methods (Table 4) specifies GSS-API-authenticated Elliptic Curve Diffie-Hellman key exchanges as described in Section 5.1. The method name for each method (Table 3) is the concatenation of the family method name with the base64 encoding of the MD5 hash [RFC1321] of the ASN.1 DER encoding [ISO-IEC-8825-1] of the corresponding GSS-API mechanism's OID. Base64 encoding is described in Section 4 of [RFC4648]. So the name is basically prefix plus a hashed OID, literally iykyk 🧚
+------------------------+----------+---------------+---------------+
| Family Name Prefix | Hash | Parameters / | Definition |
| | Function | Function Name | |
+========================+==========+===============+===============+
| gss-nistp256-sha256- | SHA-256 | secp256r1 | Section |
| | | | 2.4.2 of |
| | | | [SEC2v2] |
+------------------------+----------+---------------+---------------+
| gss-nistp384-sha384- | SHA-384 | secp384r1 | Section |
| | | | 2.5.1 of |
| | | | [SEC2v2] |
+------------------------+----------+---------------+---------------+
| gss-nistp521-sha512- | SHA-512 | secp521r1 | Section |
| | | | 2.6.1 of |
| | | | [SEC2v2] |
+------------------------+----------+---------------+---------------+
| gss-curve25519-sha256- | SHA-256 | X22519 | Section 5 |
| | | | of |
| | | | [RFC7748] |
+------------------------+----------+---------------+---------------+
| gss-curve448-sha512- | SHA-512 | X448 | Section 5 |
| | | | of |
| | | | [RFC7748] |
+------------------------+----------+---------------+---------------+
Table 4: Family Method References6. Deprecated Algorithms 💀
Because they have small key lengths and are no longer strong in the face of brute-force attacks, the algorithms in the following table are considered deprecated and SHOULD NOT be used. Not it 🙅♀️
+--------------------------+--------------------------------+
| Key Exchange Method Name | Implementation Recommendations |
+==========================+================================+
| gss-group1-sha1-* | SHOULD NOT |
+--------------------------+--------------------------------+
| gss-group14-sha1-* | SHOULD NOT |
+--------------------------+--------------------------------+
| gss-gex-sha1-* | SHOULD NOT |
+--------------------------+--------------------------------+
Table 5: Deprecated Algorithms7. IANA Considerations 🌈
This document augments the SSH key exchange message names that were defined in [RFC4462] (see and Section 6); IANA has listed this document as reference for those entries in the "SSH Protocol Parameters" [IANA-KEX-NAMES] registry.
In addition, IANA has updated the registry to include the SSH key exchange message names described in Sections 4 and 5.
+--------------------------+-----------+
| Key Exchange Method Name | Reference |
+==========================+===========+
| gss-group1-sha1-* | RFC 8732 |
+--------------------------+-----------+
| gss-group14-sha1-* | RFC 8732 |
+--------------------------+-----------+
| gss-gex-sha1-* | RFC 8732 |
+--------------------------+-----------+
| gss-group14-sha256-* | RFC 8732 |
+--------------------------+-----------+
| gss-group15-sha512-* | RFC 8732 |
+--------------------------+-----------+
| gss-group16-sha512-* | RFC 8732 |
+--------------------------+-----------+
| gss-group17-sha512-* | RFC 8732 |
+--------------------------+-----------+
| gss-group18-sha512-* | RFC 8732 |
+--------------------------+-----------+
| gss-nistp256-sha256-* | RFC 8732 |
+--------------------------+-----------+
| gss-nistp384-sha384-* | RFC 8732 |
+--------------------------+-----------+
| gss-nistp521-sha512-* | RFC 8732 |
+--------------------------+-----------+
| gss-curve25519-sha256-* | RFC 8732 |
+--------------------------+-----------+
| gss-curve448-sha512-* | RFC 8732 |
+--------------------------+-----------+
Table 6: Additions/Changes to the
Key Exchange Method Names Registry8. Security Considerations 🔥
8.1. New Finite Field DH Mechanisms
Except for the use of a different secure hash function and larger DH groups, no significant changes have been made to the protocol described by [RFC4462]; therefore, all the original security considerations apply.
8.2. New Elliptic Curve DH Mechanisms
Although a new cryptographic primitive is used with these methods, the actual key exchange closely follows the key exchange defined in [RFC5656]; therefore, all the original security considerations, as well as those expressed in [RFC5656], apply.
8.3. GSS-API Delegation 😭
Some GSS-API mechanisms can act on a request to delegate credentials to the target host when the deleg_req_flag is set. In this case, extra care must be taken to ensure that the acceptor being authenticated matches the target the user intended. Some mechanism implementations (such as commonly used krb5 libraries) may use insecure DNS resolution to canonicalize the target name; in these cases, spoofing a DNS response that points to an attacker-controlled machine may result in the user silently delegating credentials to the attacker, who can then impersonate the user at will.
Seriously, this one is a big deal. If the target name gets resolved over insecure DNS, an attacker can point it at their own machine, and the user can end up quietly handing their credentials over. Then the attacker can impersonate them whenever they like 💀
9. References 📚
9.1. Normative References
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743,
DOI 10.17487/RFC2743, January 2000,
<https://www.rfc-editor.org/info/rfc2743>.
[RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
Diffie-Hellman groups for Internet Key Exchange (IKE)",
RFC 3526, DOI 10.17487/RFC3526, May 2003,
<https://www.rfc-editor.org/info/rfc3526>.
[RFC4462] Hutzelman, J., Salowey, J., Galbraith, J., and V. Welch,
"Generic Security Service Application Program Interface
(GSS-API) Authentication and Key Exchange for the Secure
Shell (SSH) Protocol", RFC 4462, DOI 10.17487/RFC4462, May
2006, <https://www.rfc-editor.org/info/rfc4462>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC5656] Stebila, D. and J. Green, "Elliptic Curve Algorithm
Integration in the Secure Shell Transport Layer",
RFC 5656, DOI 10.17487/RFC5656, December 2009,
<https://www.rfc-editor.org/info/rfc5656>.
[RFC7546] Kaduk, B., "Structure of the Generic Security Service
(GSS) Negotiation Loop", RFC 7546, DOI 10.17487/RFC7546,
May 2015, <https://www.rfc-editor.org/info/rfc7546>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8731] Adamantiadis, A., Josefsson, S., and M. Baushke, "Secure
Shell (SSH) Key Exchange Method Using Curve25519 and
Curve448", RFC 8731, DOI 10.17487/RFC8731, February 2020,
<https://www.rfc-editor.org/info/rfc8731>.
[SEC1v2] Standards for Efficient Cryptography Group, "SEC 1:
Elliptic Curve Cryptography", Version 2.0, May 2009.
[SEC2v2] Standards for Elliptic Cryptography Group, "SEC 2:
Recommended Elliptic Curve Domain Parameters",
Version 2.0, January 2010.9.2. Informative References ✨
okay bestie, these are the "good to know" sources 📚 the spec leans on for background, not the must-read core. Here's the full list, every single one, exactly as written 💅
[IANA-KEX-NAMES]
IANA, "Secure Shell (SSH) Protocol Parameters: Key
Exchange Method Names",
<https://www.iana.org/assignments/ssh-parameters/>.
[ISO-IEC-8825-1]
ITU-T, "Information technology -- ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ISO/IEC 8825-1:2015, ITU-T Recommendation X.690,
November 2015,
<http://standards.iso.org/ittf/PubliclyAvailableStandards/
c068345_ISO_IEC_8825-1_2015.zip>.
[NIST-SP-800-131Ar2]
National Institute of Standards and Technology,
"Transitioning of the Use of Cryptographic Algorithms and
Key Lengths", DOI 10.6028/NIST.SP.800-131Ar2, NIST Special
Publication 800-131A Revision 2, November 2015,
<https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-131Ar2.pdf>.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
<https://www.rfc-editor.org/info/rfc6194>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC8268] Baushke, M., "More Modular Exponentiation (MODP) Diffie-
Hellman (DH) Key Exchange (KEX) Groups for Secure Shell
(SSH)", RFC 8268, DOI 10.17487/RFC8268, December 2017,
<https://www.rfc-editor.org/info/rfc8268>.Authors' Addresses 💌
the people behind this spec, and how to reach them 🦋 Simo and Hubert, you two are iconic 👑
Simo Sorce
Red Hat, Inc.
140 Broadway, 24th Floor
New York, NY 10025
United States of America
Email: simo@redhat.com
Hubert Kario
Red Hat, Inc.
Purkynova 115
612 00 Brno
Czech Republic
Email: hkario@redhat.comand that's the whole spec, bestie 🌈✨🫶
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