The specification of DomainKeys is contained in an Internet Draft from Yahoo!, Inc. More information can be found here.
This API (libdk) allows an application to sign or verify messages according to the DomainKeys proposed standard. Also provided is an implementation of a filter, using Sendmail's milter package, that uses libdk to implement this facility.
| Data Type | Description |
| DK | A signing/verifying context for a message. |
| dk_alg_t | A signature generation/verification method. |
| dk_canon_t | A canonicalization method. |
| DK_FLAGS | Flags; a union the following macros, representing flag bits: |
| DK_LIB | An instance of the libdk service. |
| dk_query_t | Query method. |
| dk_sigkey_t | Private key data. |
| DK_STAT | Return value/status. |
| Function | Description |
| Administration | |
| dk_close() | Shut down an instance of the DomainKeys service. |
| dk_init() | Initialize an instance of the DomainKeys service. |
| Signing | |
| dk_sign() | Allocate a new DomainKeys handle for signing a message. |
| dk_getsig() | Generate and return a signature. |
| dk_gethdrs() | Retrieve a list of headers included in the computation of the signature. |
| dk_getidentity() | Retrieve sender identity information extracted from headers. |
| Verifying | |
| dk_verify() | Allocate a new DomainKeys handle for verifying a message. |
| dk_reportinfo() | Retrieve information required to generate a verification failure report. (EXPERIMENTAL) |
| dkim_geterror() | Retrieve the most recent internal error message associated with a DK handle. |
| Processing | |
| dk_header() | Process a header. |
| dk_eoh() | Identify end of headers. |
| dk_body() | Process a body chunk. |
| dk_eom() | Identify end of message. |
| Utility | |
| dk_options() | Get or set library options. |
| dk_timeout() | Get or set DNS timeout value. |
| rfc2822_mailbox_split() | Parse an RFC2822 header, e.g. From:, to get user and domain. |
| Cleanup | |
| dk_free() | Destroy a per-message handle of the DomainKeys service. |