PBC Library Manual 0.5.11 - Stanford Crypto Group

Chapter 5. Param functions
Pairings are initialized from pairing parameters, which are objects of type pbc_param_t. Some
applications can ignore this data type because pairing_init_set_str() handles it behind the scenes:
it reads a string as a pbc_param_t, then initializes a pairing with these parameters.
int pbc_param_init_set_str(pbc_param_t par, const char *s)
Initializes pairing parameters from the string s. Returns 0 if successful, 1 otherwise.
int pbc_param_init_set_buf(pbc_param_t par, const char *s, size_t len)
Same, but read at most len bytes. If len is 0, it behaves as the previous function. Returns 0 if successful, 1
otherwise.
void pbc_param_out_str(FILE *stream, pbc_param_t p)
Write pairing parameters to ’stream’ in a text format.
void pbc_param_clear(pbc_param_t p)
Clear p. Call after p is no longer needed.
5.1. Param generation
These were used to prepare the sample parameters in the param subdirectory.
We label the pairing families with capital letters roughly in the order of discovery, so we can refer to
them easily. Type A is fastest. Type D is a good choice when elements should be short but is slower. Type
F has even shorter elements but is slower still. The speed differences are hardware-dependent, and also
change when preprocessing is used. Type B and C are unimplemented.
The pbc_cm_t data type holds CM parameters that are used to generate type D and G curves.
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