Cryptography standards

There are a number of standards related to cryptography. Standard algorithms and protocols provide a focus for study; standards for popular applications attract a large amount of cryptanalysis.

• Data Encryption Standard (DES, now obsolete)
• Advanced Encryption Standard (AES)
• RSA the original public key algorithm
• OpenPGP

• MD5 128-bit (obsolete)
• SHA-1 160-bit (obsolete)
• SHA-2 available in 224, 256, 384, and 512-bit variants
• HMAC keyed hash
• PBKDF2 Key derivation function (RFC 2898)

• Digital Signature Standard (DSS), based on the Digital Signature Algorithm (DSA)
• RSA
• Elliptic Curve DSA

• X.509 Public Key Certificates

• Wired Equivalent Privacy (WEP), severely flawed and superseded by WPA
• Wi-Fi Protected Access (WPA) better than WEP, a 'pre-standard' partial version of 802.11i
• 802.11i a.k.a. WPA2, uses AES and other improvements on WEP
• A5/1 and A5/2 cell phone encryption for GSM

• FIPS PUB 31 Guidelines for Automatic Data Processing Physical Security and Risk Management 1974
• FIPS PUB 46-3 Data Encryption Standard (DES) 1999
• FIPS PUB 73 Guidelines for Security of Computer Applications 1980
• FIPS PUB 74 Guidelines for Implementing and Using the NBS Data Encryption Standard 1981
• FIPS PUB 81 DES Modes of Operation 1980
• FIPS PUB 102 Guideline for Computer Security Certification and Accreditation 1983
• FIPS PUB 112 Password Usage 1985, defines 10 factors to be considered in access control systems that are based on passwords
• FIPS PUB 113 Computer Data Authentication 1985, specifies a Data Authentication Algorithm (DAA) based on DES, adopted by the Department of Treasury and the banking community to protect electronic fund transfers.
• FIPS PUB 140-2 Security Requirements for Cryptographic Modules 2001, defines four increasing security levels
• FIPS PUB 171 Key Management Using ANSI X9.17 (ANSI X9.17-1985) 1992, based on DES
• FIPS PUB 180-2 Secure Hash Standard (SHS) 2002 defines the SHA family
• FIPS PUB 181 Automated Password Generator (APG) 1993
• FIPS PUB 185 Escrowed Encryption Standard (EES) 1994, a key escrow system that provides for decryption of telecommunications when lawfully authorized.
• FIPS PUB 186-2 Digital Signature Standard (DSS) 2000
• FIPS PUB 190 Guideline for the Use of Advanced Authentication Technology Alternatives 1994
• FIPS PUB 191 Guideline for the Analysis of local area network Security 1994
• FIPS PUB 196 Entity Authentication Using Public Key Cryptography 1997
• FIPS PUB 197 Advanced Encryption Standard (AES) 2001
• FIPS PUB 198 The Keyed-Hash Message Authentication Code (HMAC) 2002

Below is a non-exhaustive overview of notable cryptography-related RFCs, grouped by topic.

Transport Security

• RFC 8446 The Transport Layer Security (TLS) Protocol Version 1.3 Defines secure web communication (HTTPS), introduces modern cipher suites and removes legacy cryptography.¹
• RFC 5246 The Transport Layer Security Protocol Version 1.2 Predecessor to TLS 1.3, still widely implemented.²

Public-Key Cryptography and Signatures

• RFC 8017 RSA Cryptography Specifications Defines RSA encryption and signature schemes such as RSA-OAEP and RSASSA-PSS.³
• RFC 6979 Specifies deterministic generation of the nonce in DSA/ECDSA to avoid catastrophic randomness failures.⁴
• RFC 7748 Defines modern elliptic curves X25519 and X448 for Diffie–Hellman key exchange.⁵

Symmetric Cryptography and MACs

• RFC 2104 Defines the HMAC construction, widely used with hash functions such as SHA-256.⁶
• RFC 5869 A widely used key derivation function used in protocols like TLS 1.3.⁷
• RFC 8439 Defines the ChaCha20 stream cipher and Poly1305 MAC AEAD construction used in TLS, SSH, and QUIC.⁸

Public-Key Infrastructure and Certificates

• RFC 5280 Defines the Internet profile for X.509 certificates, used by TLS certificate authorities.⁹
• RFC 6960 Defines a protocol for checking certificate revocation status.¹⁰

Secure Messaging and Data Formats

• RFC 5652 Defines the message format used for secure email (S/MIME).¹¹
• RFC 4880 Specifies the OpenPGP encryption and signature format used in tools like GnuPG.¹²

Network Security (IPsec)

• RFC 4301 Defines the overall IPsec security architecture.¹³
• RFC 4303 Specifies encrypted IP packets for IPsec.¹⁴
• RFC 7296 Defines key exchange and authentication for IPsec VPNs.¹⁵

• EKMS NSA's Electronic Key Management System
• FNBDT NSA's secure narrow band voice standard
• Fortezza encryption based on portable crypto token in PC Card format
• STE secure telephone
• STU-III older secure telephone
• TEMPEST prevents compromising emanations

• IPsec Virtual Private Network (VPN) and more
• IEEE P1363 covers most aspects of public-key cryptography
• Transport Layer Security (formerly SSL)
• SSH secure Telnet and more
• Content Scramble System (CSS, the DVD encryption standard, broken by DeCSS)
• Kerberos authentication standard
• RADIUS authentication standard
• ANSI X9.59 electronic payment standard
• Common Criteria Trusted operating system standard
• CRYPTREC Japanese Government's cryptography recommendations