The IETF Simple Public Key Infrastructure Working Group has defined a format
for storing, transmitting and manipulating certificates to support security
in a wide range of Internet applications which will require the use of
public key certificates.
For the definition of the SPKI format, please refer to
The format of SPKI objects is a simplified form of S-expression. An
S-expression is a list enclosed in matching "(" and ")", similar to the
recursive list data structure in of the LISP and Scheme programming
A canonical S-expression is a unique representation of an S-expression
which may contain arbitrary binary byte strings. For transport over a 7-bit
channel, it may be base64 (see
The advanced S-expression format is a complexer form of an S-expression
which is not necessarily unique. It is more suited for human reading than
the canonical S-expression format.
Examples SPKI certificates can be found in