cjdns/doc/Sign.md

Signing

Cjdns allows for signing and verification of messages using the RPC. To sign a message you need to send an authenticated RPC message to Sign_sign() RPC endpoint and to verify, you send a request (authentication not necessary) to Sign_checkSig().

Sign_sign()

Sign_sign() has 1 parameter:

• msgHash: string: is a short string (less than or equal to 64 bytes).

If you have a large message to sign, you should instead hash the message and sign the hash. Sign_sign() uses the private key of the cjdns node to sign with.

Result:

• error: string: "none" or a string representing the error
• signature: string (optional): the signature in a printable format, missing if there is an error.

Example of signing

user@underscore cjdns % ./tools/cexec 'Sign_sign("test message")'
{
  "error": "none",
  "signature": "0ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1_y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0r0hc30",
}

Sign_checkSig()

Sign_checkSig() verifies a signature, it takes 2 parameters:

• signature: string: The signature produced by Sign_sign()
• msgHash: string: The original message hash that was signed.

Result:

• error: string: "none" or a string representing the error
• ipv6: string (optional): If the signature is valid, the cjdns IPv6 address of the signer.
• pubkey: string (optional): If the signature is valid, the pubkey of the signer.

Example of signature verification

user@underscore cjdns % ./tools/cexec 'Sign_checkSig("0ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1_y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0
r0hc30", "test message")'
{
  "error": "none",
  "ipv6": "fca4:aa4c:3686:6a29:e301:89a5:942c:38d3",
  "pubkey": "hwnu9u7n8v9u7rjrflhsv45q16p103c1rfx9208hnzr2tq988z90.k",
  "txid": "575360523"
}

Example with wrong message

user@underscore cjdns % ./tools/cexec 'Sign_checkSig("0ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1_y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0
r0hc30", "not the right message")'                                       
{                                                                                                     
  "error": "invalid signature",                                                      
  "txid": "828277386"
}

Examples with corrupt signature

The last character of the signature was changed to an x

user@underscore cjdns % ./tools/cexec 'Sign_checkSig("0ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1_y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0
r0hc3x", "test message")'                                                
{                                                                        
  "error": "malformed signature, failed to decode signature",
  "txid": "1892499317"
}

The separator _ was replaced with +

user@underscore cjdns % ./tools/cexec 'Sign_checkSig("0ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1+y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0
r0hc30", "test message")'                                                
{ 
  "error": "malformed signature, missing separator",
  "txid": "1193071367"
}

The first character of the signature was replaced with a _

user@underscore cjdns % ./tools/cexec 'Sign_checkSig("_ytl2njc1hy86tlxtc2zc3449up47uqb0u04kcy233d7zrn2cwh1_y96duzwpvmslj8b7pnk2b32m0rhs738yujwtrtlcq81r0u114svygwn56phn9yncpyzhswpj3bd808lgd5bknlj8xwf7purl0
r0hc30", "test message")'
{
  "error": "malformed signature, failed to decode pubkey",
  "txid": "2668454052"
}