[#CKey-SignCompact]
= xref:CKey.adoc[CKey]::SignCompact
:relfileprefix: ../
:mrdocs:

Create a compact signature (65 bytes), which allows reconstructing the used public key. The format is one header byte, followed by two times 32 bytes for the serialized r and s values. The header byte: 0x1B = first key with even y, 0x1C = first key with odd y, 0x1D = second key with even y, 0x1E = second key with odd y, add 0x04 for compressed keys.

== Synopsis

Declared in `<key.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
bool
SignCompact(
    xref:uint256.adoc[uint256] const& hash,
    std::vector<unsigned char>& vchSig) const;
----

== Return Value

true if signing succeeded.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *hash*
| The 32‐byte message hash to sign.
| *vchSig*
| Output buffer receiving the 65‐byte compact signature.
|===


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