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Applications RFC Request for Comments I-D Internet-Draft Assertion Claim Simple Web Token Security Token SWT JavaScript Object Notation JSON JSON Web Token JWT JSON Web Signature JWS JSON Web Encryption JWE JSON Web Token (JWT) is a means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is digitally signed using a JSON Web Signature (JWS) and optionally encrypted using JSON Web Encryption (JWE). The suggested pronunciation of JWT is the same as the English word "jot". The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

JSON Web Token (JWT) is a compact token format intended for space constrained environments such as HTTP Authorization headers and URI query parameters. JWTs encode claims to be transmitted as a JSON object (as defined in RFC 4627) that is base64url encoded and digitally signed. Signing is accomplished using a JSON Web Signature (JWS) . JWTs may also be optionally encrypted using JSON Web Encryption (JWE) . The suggested pronunciation of JWT is the same as the English word "jot".

A string consisting of three JWT Token Segments: the JWT Header Segment, the JWT Claim Segment, and the JWT Crypto Segment, in that order, with the segments being separated by period ('.') characters. One of the three parts that make up a JSON Web Token (JWT). JWT Token Segments are always base64url encoded values. A JWT Token Segment containing a base64url encoded JSON object that describes the cryptographic operations applied to the JWT Header Segment and the JWT Claim Segment. The JWT Header Segment is the JWS Header Input for creating a JSON Web Signature (JWS) for the JWT. A JWT Token Segment containing a base64url encoded JSON object that encodes the claims contained in the JWT. The JWT Claim Segment is the JWS Payload Input for creating a JSON Web Signature (JWS) for the JWT. A JWT Token Segment containing base64url encoded cryptographic material that secures the contents of the JWT Header Segment and the JWT Claim Segment. The JWT Crypto Segment is the JWS Crypto Output for a JSON Web Signature (JWS) created for the JWT. A JWT Header Segment that has been base64url decoded back into a JSON object. A JWT Claim Segment that has been base64url decoded back into a JSON object. A JWT Crypto Segment that has been base64url decoded back into cryptographic material. The names of the members of the JSON object represented in a JWT Claim Segment. The values of the members of the JSON object represented in a JWT Claim Segment. For the purposes of this specification, this term always refers to the he URL- and filename-safe Base64 encoding described in RFC 4648, Section 5, with the '=' padding characters omitted, as permitted by Section 3.2.

JWTs represent a set of claims as a JSON object that is base64url encoded and digitally signed and optionally encrypted. As per RFC 4627 Section 2.2, the JSON object consists of zero or more name/value pairs (or members), where the names are strings and the values are arbitrary JSON values. These members are the claims represented by the JWT. The JSON object is base64url encoded to produce the JWT Claim Segment. The member names within the Decoded JWT Claim Segment are referred to as Claim Names. These names MUST be unique. The corresponding values are referred to as Claim Values. The JWT Claim Object is signed in the manner described in JSON Web Signature (JWS) and optionally encrypted in the manner described in JSON Web Encryption (JWE) . The JWT Claim Object is the JWS Payload Input. The JWT Header Object is the JWS Header Input. The JWT Crypto Segment is the corresponding JWS Crypto Output. A JWT is represented as the concatenation of the JWT Header Segment, the JWT Claim Segment, and the JWT Crypto Segment, in that order, with the segments being separated by period ('.') characters.

The following is an example of a JSON object that can be encoded to produce a JWT Claim Segment: Base64url encoding the UTF-8 representation of the JSON object yields this JWT Claim Segment: The following example JSON header object declares that the encoded object is a JSON Web Token (JWT) and the JWT Header Segment and the JWT Claim Segment are signed using the HMAC SHA-256 algorithm: Base64url encoding the UTF-8 representation of the JSON header object yields this JWT Header Segment value: Signing the UTF-8 representation of the JWT Header Segment and JWT Claim Segment with the HMAC SHA-256 algorithm and base64url encoding the result, as per , in the manner specified in , yields this JWT Crypto Segment value: Concatenating these segments in the order Header.Claims.Signature with period characters between the segments yields this complete JWT (with line breaks for display purposes only): This computation is illustrated in more detail in .

A JWT contains a set of claims represented as a base64url encoded JSON object. Note however, that the set of claims a JWT must contain to be considered valid is context-dependent and is outside the scope of this specification. When used in a security-related context, implementations MUST understand and support all of the claims present; otherwise, the JWT MUST be rejected for processing. There are three classes of JWT Claim Names: Reserved Claim Names, Public Claim Names, and Private Claim Names.

The following claim names are reserved. None of the claims defined in the table below are intended to be mandatory, but rather, provide a starting point for a set of useful, interoperable claims. All the names are short because a core goal of JWTs is for the tokens to be compact. Claim Name JSON Value Type Claim Syntax Claim Semantics exp integer IntDate The exp (expiration time) claim identifies the expiration time on or after which the token MUST NOT be accepted for processing. The processing of the exp claim requires that the current date/time MUST be before the expiration date/time listed in the exp claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. This claim is OPTIONAL. iat integer IntDate The iat (issued at) claim identifies the UTC time at which the JWT was issued. The processing of the iat claim requires that the current date/time MUST be after the issued date/time listed in the iat claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. This claim is OPTIONAL. iss string StringAndURI The iss (issuer) claim identifies the principal that issued the JWT. The processing of this claim is generally application specific. The iss value is case sensitive. This claim is OPTIONAL. aud string StringAndURI The aud (audience) claim identifies the audience that the JWT is intended for. The principal intended to process the JWT MUST be identified by the value of the audience claim. If the principal processing the claim does not identify itself with the identifier in the aud claim value then the JWT MUST be rejected. The interpretation of the contents of the audience value is generally application specific. The aud value is case sensitive. This claim is OPTIONAL. typ string String The typ (type) claim is used to declare a type for the contents of this JWT. The typ value is case sensitive. This claim is OPTIONAL. Additional reserved claim names MAY be defined via the IANA JSON Web Token Claims registry, as per . The syntax values used above are defined as follows: Syntax Name Syntax Definition IntDate The number of seconds from 1970-01-01T0:0:0Z as measured in UTC until the desired date/time. See RFC 3339 for details regarding date/times in general and UTC in particular. String Any string value MAY be used. StringAndURI Any string value MAY be used but a value containing a ":" character MUST be a URI as defined in RFC 3986.

Claim names can be defined at will by those using JWTs. However, in order to prevent collisions, any new claim name SHOULD either be defined in the IANA JSON Web Token Claims registry or be defined as a URI that contains a collision resistant namespace. Examples of collision resistant namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X 660 and X 670 Recommendation series or Universally Unique IDentifier (UUID) as defined in RFC 4122. In each case, the definer of the name or value MUST take reasonable precautions to make sure they are in control of the part of the namespace they use to define the claim name.

A producer and consumer of a JWT may agree to any claim name that is not a Reserved Name or a Public Name . Unlike Public Names, these private names are subject to collision and should be used with caution.

The members of the JSON object represented by the Decoded JWT Header Segment describe the cryptographic operations applied to the JWT Header Segment and the JWT Claim Segment and optionally, additional properties of the JWT. The JWT Header Segment is used as the JWS Header Input for signing. The format of the header and the cryptographic operations applied MUST be as specified in JSON Web Signature (JWS) and JSON Web Encryption (JWE) . Implementations MUST understand the entire contents of the header; otherwise, the JWT MUST be rejected for processing. JWS Header Parameters are defined by . This specification further specifies the use of the following header parameters when the JWS Header Input is a JWT Header Segment. Header Parameter Name JSON Value Type Header Parameter Syntax Header Parameter Semantics typ string String The typ (type) header parameter MAY be used to declare that this data structure is a JWT. If a typ parameter is present, it is RECOMMENDED that its value be either "JWT" or "http://openid.net/specs/jwt/1.0". Use of this header parameter is OPTIONAL.

To create a JWT, one MUST follow these steps: Create a JSON object containing the desired claims. Note that white space is explicitly allowed in the representation and no canonicalization is performed before encoding. Translate this JSON object's Unicode code points into UTF-8, as defined in RFC 3629. This is the Decoded JWT Claim Segment. Base64url encode the Decoded JWT Claim Segment. This encoding becomes the JWT Claim Segment. Create a JSON object containing a set of desired header parameters that conform to the and specifications. Note that white space is explicitly allowed in the representation and no canonicalization is performed before encoding. Translate this JSON object's Unicode code points into UTF-8, as defined in RFC 3629. This is the Decoded JWT Header Segment. Base64url encode the UTF-8 representation of this JSON object as defined in this specification (without padding). This encoding becomes a JWT Header Segment. Unless the alg value is none, sign and optionally encrypt the JWT Header Segment and JWT Claim Segment values in the manner described in the and specifications; the JWT Header Segment is used as the JWS Header Input and the JWT Claim Segment is used as the JWS Payload Input; the resulting JWS Crypto Output is used as the JWT Claim Segment. Otherwise, if the alg value is none, the JWT Crypto Segment is the empty string. Concatenate the JWT Header Segment, the JWT Claim Segment, and the JWT Crypto Segment in that order, separating each by period characters, to create the JWT. When validating a JWT the following steps MUST be taken. If any of the listed steps fails then the token MUST be rejected for processing. The JWT MUST contain two period characters. The JWT MUST be split on the two period characters resulting in three segment strings. The first segment is the JWT Header Segment; the second is the JWT Claim Segment; the third is the JWT Crypto Segment. The JWT Claim Segment MUST be successfully base64url decoded following the restriction given in this specification that no padding characters have been used. The Decoded JWT Claim Segment MUST be completely valid JSON syntax conforming to RFC 4627. When used in a security-related context, the Decoded JWT Claim Segment MUST be validated to only include claims whose syntax and semantics are both understood and supported. The JWT Header Segment MUST be successfully base64url decoded following the restriction given in this specification that no padding characters have been used. The Decoded JWT Header Segment MUST be completely valid JSON syntax conforming to RFC 4627. The JWT Crypto Segment MUST be successfully base64url decoded following the restriction given in this specification that no padding characters have been used. The JWT Header Segment MUST be validated to only include parameters and values whose syntax and semantics are both understood and supported. Unless the alg value is none, the JWT Crypto Segment MUST be successfully validated against the JWT Header Segment and JWT Claim Segment in the manner defined by the and specifications; otherwise the JWT Crypto Segment MUST be the empty string. Processing a JWT inevitably requires comparing known strings to values in the token. For example, in checking what the algorithm is, the Unicode string encoding alg will be checked against the member names in the Decoded JWT Header Segment to see if there is a matching header parameter name. A similar process occurs when determining if the value of the alg header parameter represents a supported algorithm. Comparing Unicode strings, however, has significant security implications, as per . Comparisons between JSON strings and other Unicode strings MUST be performed as specified below: Remove any JSON applied escaping to produce an array of Unicode code points. Unicode Normalization MUST NOT be applied at any point to either the JSON string or to the string it is to be compared against. Comparisons between the two strings MUST be performed as a Unicode code point to code point equality comparison.

JWTs make use of the base64url encoding as defined in RFC 4648. As allowed by Section 3.2 of the RFC, this specification mandates that base64url encoding when used with JWTs MUST NOT use padding. The reason for this restriction is that the padding character ('=') is not URL safe. For notes on implementing base64url encoding without padding, see .

JWTs use JSON Web Signatures (JWSs) and JSON Web Encryption (JWE) to sign and optionally encrypt the contents of the JWT Header Segment and the JWT Claim Segment to produce the JWT Crypto Segment Value. Of the JWS signing algorithms, only HMAC SHA-256 MUST be implemented by conforming JWT implementations. It is RECOMMENDED that implementations also support the RSA SHA-256 and ECDSA P-256 SHA-256 algorithms. Support for other algorithms is OPTIONAL.

To support use cases where the JWT content is secured by a means other than a signature contained within the token (such as signature on a data structure containing the token), JWTs MAY also be created without a signature. Unsigned JWTs MUST use the alg value none and use the empty string as the JWT Crypto Segment value.

This specification calls for: A new IANA registry entitled "JSON Web Token Claims" for reserved claim names is defined in . Inclusion in the registry is RFC Required in the RFC 5226 sense for reserved JWT claim names that are intended to be interoperable between implementations. The registry will just record the reserved claim name and a pointer to the RFC that defines it. This specification defines inclusion of the claim names defined in .

TBD: Lots of work to do here. We need to remember to look into any issues relating to security and JSON parsing. One wonders just how secure most JSON parsing libraries are. Were they ever hardened for security scenarios? If not, what kind of holes does that open up? Also, we need to walk through the JSON standard and see what kind of issues we have especially around comparison of names. For instance, comparisons of claim names and other parameters must occur after they are unescaped. Need to also put in text about: Importance of keeping secrets secret. Rotating keys. Strengths and weaknesses of the different algorithms. TBD: Need to put in text about why strict JSON validation is necessary. Basically, that if malformed JSON is received then the intent of the sender is impossible to reliably discern. While in non-security contexts it's o.k. to be generous in what one accepts, in security contexts this can lead to serious security holes. For example, malformed JSON might indicate that someone has managed to find a security hole in the issuer's code and is leveraging it to get the issuer to issue "bad" tokens whose content the attacker can control. TBD: Write about need to secure token content if a signature is not contained in the JWT itself.

Claim names in JWTs are Unicode strings. For security reasons, the representations of these names must be compared verbatim after performing any escape processing (as per RFC 4627, Section 2.5). This means, for instance, that these JSON strings must compare as being equal ("JWT", "\u004aWT"), whereas these must all compare as being not equal to the first set or to each other ("jwt", "Jwt", "JW\u0074"). JSON strings MAY contain characters outside the Unicode Basic Multilingual Plane. For instance, the G clef character (U+1D11E) may be represented in a JSON string as "\uD834\uDD1E". Ideally, JWT implementations SHOULD ensure that characters outside the Basic Multilingual Plane are preserved and compared correctly; alternatively, if this is not possible due to these characters exercising limitations present in the underlying JSON implementation, then input containing them MUST be rejected.

The following items remain to be done in this draft (and related drafts): Consider whether we really want to allow private claim names and that are not registered with IANA and are not in collision-resistant namespaces. Eventually this could result in interop nightmares where you need to have different code to talk to different endpoints that "knows" about each endpoints' private parameters. Clarify the optional ability to provide type information for JWTs and/or their segments. Specifically, clarify the intended use of the typ Header Parameter and the typ claim, whether they convey syntax or semantics, and indeed, whether this is the right approach. Also clarify the relationship between these type values and MIME types. Finish the Security Considerations section. Sort out what to do with the IANA registries if this is first standardized as an OpenID specification. Write a companion specification that contains the former JWT JSON Serialization.

&RFC2045; &rfc2119; &RFC3339; &RFC3629; &RFC3986; &RFC4627; &RFC4648; &RFC5226;

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This section provides several examples of JWTs. The cryptographic operations for these examples are detailed in the JSON Web Signature (JWS) specification.

The Decoded JWT Claim Segment used in this example is: Note that white space is explicitly allowed in Decoded JWT Claim Segments and no canonicalization is performed before encoding. The following byte array contains the UTF-8 characters for the Decoded JWT Claim Segment: [123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10, 32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56, 48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97, 109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111, 111, 116, 34, 58, 116, 114, 117, 101, 125] Base64url encoding the above yields the JWT Claim Segment value: The following example JSON header object declares that the data structure is a JSON Web Token (JWT) and the JWT Header Segment and JWT Crypto Segment are signed using the HMAC SHA-256 algorithm: The following byte array contains the UTF-8 characters for the Decoded JWT Header Segment: [123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32, 34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125] Base64url encoding this UTF-8 representation yields this JWT Header Segment value: This example uses the key represented by the following byte array: [3, 35, 53, 75, 43, 15, 165, 188, 131, 126, 6, 101, 119, 123, 166, 143, 90, 179, 40, 230, 240, 84, 201, 40, 169, 15, 132, 178, 210, 80, 46, 191, 211, 251, 90, 146, 210, 6, 71, 239, 150, 138, 180, 195, 119, 98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103, 208, 128, 163] Signing the JWT Header Segment and JWT Claim Segment with this key in the manner specified by yields this JWT Crypto Segment value: Combining these segments in the order Header.Claims.Signature with period characters between the segments yields this complete JWT (with line breaks for display purposes only):

The Decoded JWT Claim Segment used in this example is the same as in the previous example: Since the JWT Claim Segment will therefore be the same, its computation is not repeated here. However, the Decoded JWT Header Segment is different in two ways: First, because a different algorithm is being used, the alg value is different. Second, for illustration purposes only, the optional "typ" parameter is not used. (This difference is not related to the signature algorithm employed.) The Decoded JWT Header Segment used is: The following byte array contains the UTF-8 characters for the Decoded JWT Header Segment: [123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125] Base64url encoding this UTF-8 representation yields this JWT Header Segment value: The RSA key consists of a public part (n, e), and a private exponent d. The values of the RSA key used in this example, presented as the byte arrays representing big endian integers are: Parameter Name Value n [161, 248, 22, 10, 226, 227, 201, 180, 101, 206, 141, 45, 101, 98, 99, 54, 43, 146, 125, 190, 41, 225, 240, 36, 119, 252, 22, 37, 204, 144, 161, 54, 227, 139, 217, 52, 151, 197, 182, 234, 99, 221, 119, 17, 230, 124, 116, 41, 249, 86, 176, 251, 138, 143, 8, 154, 220, 75, 105, 137, 60, 193, 51, 63, 83, 237, 208, 25, 184, 119, 132, 37, 47, 236, 145, 79, 228, 133, 119, 105, 89, 75, 234, 66, 128, 211, 44, 15, 85, 191, 98, 148, 79, 19, 3, 150, 188, 110, 155, 223, 110, 189, 210, 189, 163, 103, 142, 236, 160, 198, 104, 247, 1, 179, 141, 191, 251, 56, 200, 52, 44, 226, 254, 109, 39, 250, 222, 74, 90, 72, 116, 151, 157, 212, 185, 207, 154, 222, 196, 199, 91, 5, 133, 44, 44, 15, 94, 248, 165, 193, 117, 3, 146, 249, 68, 232, 237, 100, 193, 16, 198, 182, 71, 96, 154, 164, 120, 58, 235, 156, 108, 154, 215, 85, 49, 48, 80, 99, 139, 131, 102, 92, 111, 111, 122, 130, 163, 150, 112, 42, 31, 100, 27, 130, 211, 235, 242, 57, 34, 25, 73, 31, 182, 134, 135, 44, 87, 22, 245, 10, 248, 53, 141, 154, 139, 157, 23, 195, 64, 114, 143, 127, 135, 216, 154, 24, 216, 252, 171, 103, 173, 132, 89, 12, 46, 207, 117, 147, 57, 54, 60, 7, 3, 77, 111, 96, 111, 158, 33, 224, 84, 86, 202, 229, 233, 161] e [1, 0, 1] d [18, 174, 113, 164, 105, 205, 10, 43, 195, 126, 82, 108, 69, 0, 87, 31, 29, 97, 117, 29, 100, 233, 73, 112, 123, 98, 89, 15, 157, 11, 165, 124, 150, 60, 64, 30, 63, 207, 47, 44, 211, 189, 236, 136, 229, 3, 191, 198, 67, 155, 11, 40, 200, 47, 125, 55, 151, 103, 31, 82, 19, 238, 216, 193, 90, 37, 216, 213, 206, 160, 2, 94, 227, 171, 46, 139, 127, 121, 33, 111, 198, 59, 234, 86, 39, 83, 180, 6, 68, 198, 161, 81, 39, 217, 178, 149, 69, 64, 160, 187, 225, 163, 5, 86, 152, 45, 78, 159, 222, 95, 100, 37, 241, 77, 75, 113, 52, 65, 181, 93, 199, 59, 155, 74, 237, 204, 146, 172, 227, 146, 126, 55, 245, 125, 12, 253, 94, 117, 129, 250, 81, 44, 143, 73, 97, 169, 235, 11, 128, 248, 168, 7, 70, 114, 138, 85, 255, 70, 71, 31, 52, 37, 6, 59, 157, 83, 100, 47, 94, 222, 30, 132, 214, 19, 8, 26, 250, 92, 34, 208, 81, 40, 91, 214, 59, 148, 59, 86, 93, 137, 138, 5, 104, 84, 19, 229, 60, 60, 108, 101, 37, 255, 31, 227, 78, 61, 220, 112, 240, 213, 100, 80, 253, 164, 139, 161, 46, 16, 78, 157, 235, 159, 184, 24, 129, 225, 196, 189, 242, 93, 146, 71, 244, 80, 200, 101, 146, 121, 104, 231, 115, 52, 244, 65, 79, 117, 167, 80, 225, 57, 84, 110, 58, 138, 115, 157] Signing the JWT Header Segment and JWT Claim Segment with this key in the manner specified by yields this JWT Crypto Segment value: Combining these segments in the order Header.Claims.Signature with period characters between the segments yields this complete JWT (with line breaks for display purposes only):

The Decoded JWT Claim Segment used in this example is the same as in the previous examples: Since the JWT Claim Segment will therefore be the same, its computation is not repeated here. However, the Decoded JWT Header Segment is differs from the previous example because a different algorithm is being used. The Decoded JWT Header Segment used is: The following byte array contains the UTF-8 characters for the Decoded JWT Header Segment: [123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125] Base64url encoding this UTF-8 representation yields this JWT Header Segment value: The ECDSA key consists of a public part, the EC point (x, y), and a private part d. The values of the ECDSA key used in this example, presented as the byte arrays representing big endian integers are: Parameter Name Value x [127, 205, 206, 39, 112, 246, 196, 93, 65, 131, 203, 238, 111, 219, 75, 123, 88, 7, 51, 53, 123, 233, 239, 19, 186, 207, 110, 60, 123, 209, 84, 69] y [199, 241, 68, 205, 27, 189, 155, 126, 135, 44, 223, 237, 185, 238, 185, 244, 179, 105, 93, 110, 169, 11, 36, 173, 138, 70, 35, 40, 133, 136, 229, 173] d [142, 155, 16, 158, 113, 144, 152, 191, 152, 4, 135, 223, 31, 93, 119, 233, 203, 41, 96, 110, 190, 210, 38, 59, 95, 87, 194, 19, 223, 132, 244, 178] Signing the JWT Header Segment and JWT Claim Segment with this key in the manner specified by yields this JWT Crypto Segment value: Combining these segments in the order Header.Claims.Signature with period characters between the segments yields this complete JWT (with line breaks for display purposes only):

This appendix describes how to implement base64url encoding and decoding functions without padding based upon standard base64 encoding and decoding functions that do use padding. To be concrete, example C# code implementing these functions is shown below. Similar code could be used in other languages. As per the example code above, the number of '=' padding characters that needs to be added to the end of a base64url encoded string without padding to turn it into one with padding is a deterministic function of the length of the encoded string. Specifically, if the length mod 4 is 0, no padding is added; if the length mod 4 is 2, two '=' padding characters are added; if the length mod 4 is 3, one '=' padding character is added; if the length mod 4 is 1, the input is malformed. An example correspondence between unencoded and encoded values follows. The byte sequence below encodes into the string below, which when decoded, reproduces the byte sequence. 3 236 255 224 193 A-z_4ME

SAML 2.0 provides a standard for creating tokens with much greater expressivity and more security options than supported by JWTs. However, the cost of this flexibility and expressiveness is both size and complexity. In addition, SAML's use of XML and XML DSIG only contributes to the size of SAML tokens. JWTs are intended to provide a simple token format that is small enough to fit into HTTP headers and query arguments in URIs. It does this by supporting a much simpler token model than SAML and using the JSON object encoding syntax. It also supports securing tokens using Hash-based Message Authentication Codes (HMACs) and digital signatures using a smaller (and less flexible) format than XML DSIG. Therefore, while JWTs can do some of the things SAML tokens do, JWTs are not intended as a full replacement for SAML tokens, but rather as a compromise token format to be used when space is at a premium.

Both JWTs and Simple Web Tokens SWT, at their core, enable sets of claims to be communicated between applications. For SWTs, both the claim names and claim values are strings. For JWTs, while claim names are strings, claim values can be any JSON type. Both token types offer cryptographic protection of their content: SWTs with HMAC SHA-256 and JWTs with a choice of algorithms, including HMAC SHA-256, RSA SHA-256, and ECDSA P-256 SHA-256.

The authors acknowledge that the design of JWTs was intentionally influenced by the design and simplicity of Simple Web Tokens and ideas for JSON tokens that Dick Hardt discussed within the OpenID community. Solutions for signing JSON content were previously explored by Magic Signatures, JSON Simple Sign, and Canvas Applications, all of which influenced this draft.

-04 Correct typo found by John Bradley: "the JWT Claim Segment is the empty string" -> "the JWT Crypto Segment is the empty string". -03 Added "http://openid.net/specs/jwt/1.0" as a token type identifier URI for JWTs. Added iat (issued at) claim. Changed RSA SHA-256 from MUST be supported to RECOMMENDED that it be supported. Rationale: Several people have objected to the requirement for implementing RSA SHA-256, some because they will only be using HMACs and symmetric keys, and others because they only want to use ECDSA when using asymmetric keys, either for security or key length reasons, or both. Defined alg value none to represent unsigned JWTs. -02 Split signature specification out into separate draft-jones-json-web-signature-00. This split introduced no semantic changes. The JWT Compact Serialization is now the only token serialization format specified in this draft. The JWT JSON Serialization can continue to be defined in a companion specification. -01 Draft incorporating consensus decisions reached at IIW. -00 Public draft published before November 2010 IIW based upon the JSON token convergence proposal incorporating input from several implementers of related specifications.