CODEWITHSUNDEEP
jwtjwkjose4jnimbus-jose-jwt
samshers
samshers

Reputation: 3660

What does "e": "AQAB" mean in jwks?

What does "e": "AQAB" mean in JWKS - Json Web Key Set

{
  "keys": [
    {
      "kty": "RSA", #key type
      "e": "AQAB",  #Question - what does "e" mean or stand for. And what values can e take. What is AQAB here. 
      "use": "sig", #verify client assertion signature. This means what is the use of the key. Answer - to verify signature. Right?
      "kid": "somebase64encodestring", #key id
      "alg": "RS256",  #key algoritham. Here it is RSA.
      "n": "anotherbase64encodestring"  #This is the actual public key base64 encoded.
    }
  ]
}

Upvotes: 16

Views: 12915

Answers (1)

Brian Campbell
Brian Campbell

Reputation: 2461

It's part of the public key too. From https://datatracker.ietf.org/doc/html/rfc7518#section-6.3.1.2

6.3.1.2. "e" (Exponent) Parameter

The "e" (exponent) parameter contains the exponent value for the RSA public key. It is represented as a Base64urlUInt-encoded value.

For instance, when representing the value 65537, the octet sequence to be base64url-encoded MUST consist of the three octets [1, 0, 1]; the resulting representation for this value is "AQAB".

Example on Bash command line:
Decimal 65537 => converts to hexadecimal 0x010001 => encodes to Base64 AQAB like so:

$ printf '%06x' 65537 | xxd -r -p | xxd
00000000: 0100 01                                  ...

$ printf '%06x' 65537 | xxd -r -p | base64
AQAB

Upvotes: 14

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