Format of colon listings ======================== First an example: $ gpg --fixed-list-mode --with-colons --list-keys \ --with-fingerprint --with-fingerprint wk@gnupg.org pub:f:1024:17:6C7EE1B8621CC013:899817715:1055898235::m:::scESC: fpr:::::::::ECAF7590EB3443B5C7CF3ACB6C7EE1B8621CC013: uid:f::::::::Werner Koch : uid:f::::::::Werner Koch : sub:f:1536:16:06AD222CADF6A6E1:919537416:1036177416:::::e: fpr:::::::::CF8BCC4B18DE08FCD8A1615906AD222CADF6A6E1: sub:r:1536:20:5CE086B5B5A18FF4:899817788:1025961788:::::esc: fpr:::::::::AB059359A3B81F410FCFF97F5CE086B5B5A18FF4: The double --with-fingerprint prints the fingerprint for the subkeys too, --fixed-list-mode is themodern listing way printing dates in seconds since Epoch and does not merge the first userID with the pub record. 1. Field: Type of record pub = public key crt = X.509 certificate crs = X.509 certificate and private key available sub = subkey (secondary key) sec = secret key ssb = secret subkey (secondary key) uid = user id (only field 10 is used). uat = user attribute (same as user id except for field 10). sig = signature rev = revocation signature fpr = fingerprint: (fingerprint is in field 10) pkd = public key data (special field format, see below) grp = reserved for gpgsm rvk = revocation key tru = trust database information 2. Field: A letter describing the calculated trust. This is a single letter, but be prepared that additional information may follow in some future versions. (not used for secret keys) o = Unknown (this key is new to the system) i = The key is invalid (e.g. due to a missing self-signature) d = The key has been disabled (deprecated - use the 'D' in field 12 instead) r = The key has been revoked e = The key has expired - = Unknown trust (i.e. no value assigned) q = Undefined trust '-' and 'q' may safely be treated as the same value for most purposes n = Don't trust this key at all m = There is marginal trust in this key f = The key is fully trusted u = The key is ultimately trusted. This often means that the secret key is available, but any key may be marked as ultimately trusted. 3. Field: length of key in bits. 4. Field: Algorithm: 1 = RSA 16 = ElGamal (encrypt only) 17 = DSA (sometimes called DH, sign only) 20 = ElGamal (sign and encrypt) (for other id's see include/cipher.h) 5. Field: KeyID 6. Field: Creation Date (in UTC). For UID and UAT records, this is the self-signature date. 7. Field: Key or user ID/user attribute expiration date or empty if none. 8. Field: Used for serial number in crt records (used to be the Local-ID). For UID and UAT records, this is a hash of the user ID contents used to represent that exact user ID. For trust signatures, this is the trust depth seperated by the trust value by a space. 9. Field: Ownertrust (primary public keys only) This is a single letter, but be prepared that additional information may follow in some future versions. For trust signatures with a regular expression, this is the regular expression value, quoted as in field 10. 10. Field: User-ID. The value is quoted like a C string to avoid control characters (the colon is quoted "\x3a"). This is not used with --fixed-list-mode in gpg. A UAT record puts the attribute subpacket count here, a space, and then the total attribute subpacket size. In gpgsm the issuer name comes here An FPR record stores the fingerprint here. The fingerprint of an revocation key is stored here. 11. Field: Signature class. This is a 2 digit hexnumber followed by either the letter 'x' for an exportable signature or the letter 'l' for a local-only signature. The class byte of an revocation key is also given here, 'x' and 'l' ist used the same way. 12. Field: Key capabilities: e = encrypt s = sign c = certify A key may have any combination of them in any order. In addition to these letters, the primary key has uppercase versions of the letters to denote the _usable_ capabilities of the entire key, and a potential letter 'D' to indicate a disabled key. 13. Field: Used in FPR records for S/MIME keys to store the fingerprint of the issuer certificate. This is useful to build the certificate path based on certificates stored in the local keyDB; it is only filled if the issue certificate is available. The advantage of using this value is that it is guaranteed to have been been build by the same lookup algorithm as gpgsm uses. For "uid" recods this lists the preferences n the sameway the -edit menu does. For "sig" records, this is the fingerprint of the key that issued the signature. Note that this is only filled in if the signature verified correctly. Note also that for various technical reasons, this fingerprint is only available if --no-sig-cache is used. 14. Field Flag field used in the --edit menu output: All dates are displayed in the format yyyy-mm-dd unless you use the option --fixed-list-mode in which case they are displayed as seconds since Epoch. More fields may be added later, so parsers should be prepared for this. When parsing a number the parser should stop at the first non-number character so that additional information can later be added. If field 1 has the tag "pkd", a listing looks like this: pkd:0:1024:B665B1435F4C2 .... FF26ABB: ! ! !-- the value ! !------ for information number of bits in the value !--------- index (eg. DSA goes from 0 to 3: p,q,g,y) The "tru" trust database records have the fields: 1: Reason for staleness of trust. If this field is empty, then the trustdb is not stale. This field may have multiple flags in it: o: Trustdb is old t: Trustdb was built with a different trust model than the one we are using now. 2: Trust model. This is always zero (i.e. "Classic") in this version of GnuPG. 3: Date trustdb was created in seconds since 1/1/1970. 4: Date trustdb will expire in seconds since 1/1/1970. Format of the "--status-fd" output ================================== Every line is prefixed with "[GNUPG:] ", followed by a keyword with the type of the status line and a some arguments depending on the type (maybe none); an application should always be prepared to see more arguments in future versions. GOODSIG The signature with the keyid is good. For each signature only one of the three codes GOODSIG, BADSIG or ERRSIG will be emitted and they may be used as a marker for a new signature. The username is the primary one encoded in UTF-8 and %XX escaped. EXPSIG The signature with the keyid is good, but the signature is expired. The username is the primary one encoded in UTF-8 and %XX escaped. EXPKEYSIG The signature with the keyid is good, but the signature was made by an expired key. The username is the primary one encoded in UTF-8 and %XX escaped. REVKEYSIG The signature with the keyid is good, but the signature was made by a revoked key. The username is the primary one encoded in UTF-8 and %XX escaped. BADSIG The signature with the keyid has not been verified okay. The username is the primary one encoded in UTF-8 and %XX escaped. ERRSIG \ It was not possible to check the signature. This may be caused by a missing public key or an unsupported algorithm. A RC of 4 indicates unknown algorithm, a 9 indicates a missing public key. The other fields give more information about this signature. sig_class is a 2 byte hex-value. VALIDSIG The signature with the keyid is good. This is the same as GOODSIG but has the fingerprint as the argument. Both status lines are emitted for a good signature. All arguments here are on one long line. sig-timestamp is the signature creation time in seconds after the epoch. expire-timestamp is the signature expiration time in seconds after the epoch (zero means "does not expire"). sig-version, pubkey-algo, hash-algo, and sig-class (a 2-byte hex value) are all straight from the signature packet. PRIMARY-KEY-FPR is the fingerprint of the primary key or identical to the first argument. This is useful to get back to the primary key without running gpg again for this purpose. SIG_ID This is emitted only for signatures of class 0 or 1 which have been verified okay. The string is a signature id and may be used in applications to detect replay attacks of signed messages. Note that only DLP algorithms give unique ids - others may yield duplicated ones when they have been created in the same second. ENC_TO The message is encrypted to this keyid. keytype is the numerical value of the public key algorithm, keylength is the length of the key or 0 if it is not known (which is currently always the case). NODATA No data has been found. Codes for what are: 1 - No armored data. 2 - Expected a packet but did not found one. 3 - Invalid packet found, this may indicate a non OpenPGP message. You may see more than one of these status lines. UNEXPECTED Unexpected data has been encountered 0 - not further specified 1 TRUST_UNDEFINED TRUST_NEVER TRUST_MARGINAL TRUST_FULLY TRUST_ULTIMATE For good signatures one of these status lines are emitted to indicate how trustworthy the signature is. The error token values are currently only emiited by gpgsm. SIGEXPIRED This is deprecated in favor of KEYEXPIRED. KEYEXPIRED The key has expired. expire-timestamp is the expiration time in seconds after the epoch. KEYREVOKED The used key has been revoked by its owner. No arguments yet. BADARMOR The ASCII armor is corrupted. No arguments yet. RSA_OR_IDEA The IDEA algorithms has been used in the data. A program might want to fallback to another program to handle the data if GnuPG failed. This status message used to be emitted also for RSA but this has been dropped after the RSA patent expired. However we can't change the name of the message. SHM_INFO SHM_GET SHM_GET_BOOL SHM_GET_HIDDEN GET_BOOL GET_LINE GET_HIDDEN GOT_IT NEED_PASSPHRASE Issued whenever a passphrase is needed. keytype is the numerical value of the public key algorithm or 0 if this is not applicable, keylength is the length of the key or 0 if it is not known (this is currently always the case). NEED_PASSPHRASE_SYM Issued whenever a passphrase for symmetric encryption is needed. MISSING_PASSPHRASE No passphrase was supplied. An application which encounters this message may want to stop parsing immediately because the next message will probably be a BAD_PASSPHRASE. However, if the application is a wrapper around the key edit menu functionality it might not make sense to stop parsing but simply ignoring the following BAD_PASSPHRASE. BAD_PASSPHRASE The supplied passphrase was wrong or not given. In the latter case you may have seen a MISSING_PASSPHRASE. GOOD_PASSPHRASE The supplied passphrase was good and the secret key material is therefore usable. DECRYPTION_FAILED The symmetric decryption failed - one reason could be a wrong passphrase for a symmetrical encrypted message. DECRYPTION_OKAY The decryption process succeeded. This means, that either the correct secret key has been used or the correct passphrase for a conventional encrypted message was given. The program itself may return an errorcode because it may not be possible to verify a signature for some reasons. NO_PUBKEY NO_SECKEY The key is not available IMPORTED The keyid and name of the signature just imported IMPORT_OK [] The key with the primary key's FINGERPRINT has been imported. Reason flags: 0 := Not actually changed 1 := Entirely new key. 2 := New user IDs 4 := New signatures 8 := New subkeys 16 := Contains private key. The flags may be ORed. IMPORT_PROBLEM [] Issued for each import failure. Reason codes are: 0 := "No specific reason given". 1 := "Invalid Certificate". 2 := "Issuer Certificate missing". 3 := "Certificate Chain too long". 4 := "Error storing certificate". IMPORT_RES Final statistics on import process (this is one long line) FILE_START Start processing a file . indicates the performed operation: 1 - verify 2 - encrypt 3 - decrypt FILE_DONE Marks the end of a file processing which has been started by FILE_START. BEGIN_DECRYPTION END_DECRYPTION Mark the start and end of the actual decryption process. These are also emitted when in --list-only mode. BEGIN_ENCRYPTION END_ENCRYPTION Mark the start and end of the actual encryption process. DELETE_PROBLEM reason_code Deleting a key failed. Reason codes are: 1 - No such key 2 - Must delete secret key first 3 - Ambigious specification PROGRESS what char cur total Used by the primegen and Public key functions to indicate progress. "char" is the character displayed with no --status-fd enabled, with the linefeed replaced by an 'X'. "cur" is the current amount done and "total" is amount to be done; a "total" of 0 indicates that the total amount is not known. 100/100 may be used to detect the end of operation. SIG_CREATED A signature has been created using these parameters. type: 'D' = detached 'C' = cleartext 'S' = standard (only the first character should be checked) class: 2 hex digits with the signature class KEY_CREATED A key has been created type: 'B' = primary and subkey 'P' = primary 'S' = subkey The fingerprint is one of the primary key for type B and P and the one of the subkey for S. SESSION_KEY : The session key used to decrypt the message. This message will only be emmited when the special option --show-session-key is used. The format is suitable to be passed to the option --override-session-key NOTATION_NAME NOTATION_DATA name and string are %XX escaped; the data may be splitted among several notation_data lines. USERID_HINT Give a hint about the user ID for a certain keyID. POLICY_URL string is %XX escaped BEGIN_STREAM END_STREAM Issued by pipemode. INV_RECP Issued for each unusable recipient. The reasons codes currently in use are: 0 := "No specific reason given". 1 := "Not Found" 2 := "Ambigious specification" 3 := "Wrong key usage" 4 := "Key revoked" 5 := "Key expired" 6 := "No CRL known" 7 := "CRL too old" 8 := "Policy mismatch" 9 := "Not a secret key" 10 := "Key not trusted" Note that this status is also used for gpgsm's SIGNER command where it relates to signer's of course. NO_RECP Issued when no recipients are usable. ALREADY_SIGNED Warning: This is experimental and might be removed at any time. TRUNCATED The output was truncated to MAXNO items. This status code is issued for certain external requests ERROR This is a generic error status message, it might be followed by error location specific data. and should not contain a space. ATTRIBUTE This is one long line issued for each attribute subpacket when an attribute packet is seen during key listing. is the fingerprint of the key. is the length of the attribute subpacket. is the attribute type (1==image). / indicates that this is the Nth indexed subpacket of count total subpackets in this attribute packet. and are from the self-signature on the attribute packet. If the attribute packet does not have a valid self-signature, then the timestamp is 0. are a bitwise OR of: 0x01 = this attribute packet is a primary uid 0x02 = this attribute packet is revoked 0x04 = this attribute packet is expired Format of the "--attribute-fd" output ===================================== When --attribute-fd is set, during key listings (--list-keys, --list-secret-keys) GnuPG dumps each attribute packet to the file descriptor specified. --attribute-fd is intended for use with --status-fd as part of the required information is carried on the ATTRIBUTE status tag (see above). The contents of the attribute data is specified by 2440bis, but for convenience, here is the Photo ID format, as it is currently the only attribute defined: Byte 0-1: The length of the image header. Due to a historical accident (i.e. oops!) back in the NAI PGP days, this is a little-endian number. Currently 16 (0x10 0x00). Byte 2: The image header version. Currently 0x01. Byte 3: Encoding format. 0x01 == JPEG. Byte 4-15: Reserved, and currently unused. All other data after this header is raw image (JPEG) data. Key generation ============== Key generation shows progress by printing different characters to stderr: "." Last 10 Miller-Rabin tests failed "+" Miller-Rabin test succeeded "!" Reloading the pool with fresh prime numbers "^" Checking a new value for the generator "<" Size of one factor decreased ">" Size of one factor increased The prime number for ElGamal is generated this way: 1) Make a prime number q of 160, 200, 240 bits (depending on the keysize) 2) Select the length of the other prime factors to be at least the size of q and calculate the number of prime factors needed 3) Make a pool of prime numbers, each of the length determined in step 2 4) Get a new permutation out of the pool or continue with step 3 if we have tested all permutations. 5) Calculate a candidate prime p = 2 * q * p[1] * ... * p[n] + 1 6) Check that this prime has the correct length (this may change q if it seems not to be possible to make a prime of the desired length) 7) Check whether this is a prime using trial divisions and the Miller-Rabin test. 8) Continue with step 4 if we did not find a prime in step 7. 9) Find a generator for that prime. This algorithm is based on Lim and Lee's suggestion from the Crypto '97 proceedings p. 260. Unattended key generation ========================= This feature allows unattended generation of keys controlled by a parameter file. To use this feature, you use --gen-key together with --batch and feed the parameters either from stdin or from a file given on the commandline. The format of this file is as follows: o Text only, line length is limited to about 1000 chars. o You must use UTF-8 encoding to specify non-ascii characters. o Empty lines are ignored. o Leading and trailing spaces are ignored. o A hash sign as the first non white space character indicates a comment line. o Control statements are indicated by a leading percent sign, the arguments are separated by white space from the keyword. o Parameters are specified by a keyword, followed by a colon. Arguments are separated by white space. o The first parameter must be "Key-Type", control statements may be placed anywhere. o Key generation takes place when either the end of the parameter file is reached, the next "Key-Type" parameter is encountered or at the control statement "%commit" o Control statements: %echo Print . %dry-run Suppress actual key generation (useful for syntax checking). %commit Perform the key generation. An implicit commit is done at the next "Key-Type" parameter. %pubring %secring Do not write the key to the default or commandline given keyring but to . This must be given before the first commit to take place, duplicate specification of the same filename is ignored, the last filename before a commit is used. The filename is used until a new filename is used (at commit points) and all keys are written to that file. If a new filename is given, this file is created (and overwrites an existing one). Both control statements must be given. o The order of the parameters does not matter except for "Key-Type" which must be the first parameter. The parameters are only for the generated keyblock and parameters from previous key generations are not used. Some syntactically checks may be performed. The currently defined parameters are: Key-Type: | Starts a new parameter block by giving the type of the primary key. The algorithm must be capable of signing. This is a required parameter. Key-Length: Length of the key in bits. Default is 1024. Key-Usage: Space or comma delimited list of key usage, allowed values are "encrypt" and "sign". This is used to generate the key flags. Please make sure that the algorithm is capable of this usage. Subkey-Type: | This generates a secondary key. Currently only one subkey can be handled. Subkey-Length: Length of the subkey in bits. Default is 1024. Subkey-Usage: Similar to Key-Usage. Passphrase: If you want to specify a passphrase for the secret key, enter it here. Default is not to use any passphrase. Name-Real: Name-Comment: Name-Email: The 3 parts of a key. Remember to use UTF-8 here. If you don't give any of them, no user ID is created. Expire-Date: |([d|w|m|y]) Set the expiration date for the key (and the subkey). It may either be entered in ISO date format (2000-08-15) or as number of days, weeks, month or years. Without a letter days are assumed. Preferences: Set the cipher, hash, and compression preference values for this key. This expects the same type of string as "setpref" in the --edit menu. Revoker: : [sensitive] Add a designated revoker to the generated key. Algo is the public key algorithm of the designated revoker (i.e. RSA=1, DSA=17, etc.) Fpr is the fingerprint of the designated revoker. The optional "sensitive" flag marks the designated revoker as sensitive information. Only v4 keys may be designated revokers. Here is an example: $ cat >foo < ssb 1024g/8F70E2C0 2000-03-09 Layout of the TrustDB ===================== The TrustDB is built from fixed length records, where the first byte describes the record type. All numeric values are stored in network byte order. The length of each record is 40 bytes. The first record of the DB is always of type 1 and this is the only record of this type. FIXME: The layout changed, document it here. Record type 0: -------------- Unused record, can be reused for any purpose. Record type 1: -------------- Version information for this TrustDB. This is always the first record of the DB and the only one with type 1. 1 byte value 1 3 bytes 'gpg' magic value 1 byte Version of the TrustDB (2) 1 byte marginals needed 1 byte completes needed 1 byte max_cert_depth The three items are used to check whether the cached validity value from the dir record can be used. 1 u32 locked flags [not used] 1 u32 timestamp of trustdb creation 1 u32 timestamp of last modification which may affect the validity of keys in the trustdb. This value is checked against the validity timestamp in the dir records. 1 u32 timestamp of last validation [currently not used] (Used to keep track of the time, when this TrustDB was checked against the pubring) 1 u32 record number of keyhashtable [currently not used] 1 u32 first free record 1 u32 record number of shadow directory hash table [currently not used] It does not make sense to combine this table with the key table because the keyid is not in every case a part of the fingerprint. 1 u32 record number of the trusthashtbale Record type 2: (directory record) -------------- Informations about a public key certificate. These are static values which are never changed without user interaction. 1 byte value 2 1 byte reserved 1 u32 LID . (This is simply the record number of this record.) 1 u32 List of key-records (the first one is the primary key) 1 u32 List of uid-records 1 u32 cache record 1 byte ownertrust 1 byte dirflag 1 byte maximum validity of all the user ids 1 u32 time of last validity check. 1 u32 Must check when this time has been reached. (0 = no check required) Record type 3: (key record) -------------- Informations about a primary public key. (This is mainly used to lookup a trust record) 1 byte value 3 1 byte reserved 1 u32 LID 1 u32 next - next key record 7 bytes reserved 1 byte keyflags 1 byte pubkey algorithm 1 byte length of the fingerprint (in bytes) 20 bytes fingerprint of the public key (This is the value we use to identify a key) Record type 4: (uid record) -------------- Informations about a userid We do not store the userid but the hash value of the userid because that is sufficient. 1 byte value 4 1 byte reserved 1 u32 LID points to the directory record. 1 u32 next next userid 1 u32 pointer to preference record 1 u32 siglist list of valid signatures 1 byte uidflags 1 byte validity of the key calculated over this user id 20 bytes ripemd160 hash of the username. Record type 5: (pref record) -------------- This record type is not anymore used. 1 byte value 5 1 byte reserved 1 u32 LID; points to the directory record (and not to the uid record!). (or 0 for standard preference record) 1 u32 next 30 byte preference data Record type 6 (sigrec) ------------- Used to keep track of key signatures. Self-signatures are not stored. If a public key is not in the DB, the signature points to a shadow dir record, which in turn has a list of records which might be interested in this key (and the signature record here is one). 1 byte value 6 1 byte reserved 1 u32 LID points back to the dir record 1 u32 next next sigrec of this uid or 0 to indicate the last sigrec. 6 times 1 u32 Local_id of signatures dir or shadow dir record 1 byte Flag: Bit 0 = checked: Bit 1 is valid (we have a real directory record for this) 1 = valid is set (but may be revoked) Record type 8: (shadow directory record) -------------- This record is used to reserve a LID for a public key. We need this to create the sig records of other keys, even if we do not yet have the public key of the signature. This record (the record number to be more precise) will be reused as the dir record when we import the real public key. 1 byte value 8 1 byte reserved 1 u32 LID (This is simply the record number of this record.) 2 u32 keyid 1 byte pubkey algorithm 3 byte reserved 1 u32 hintlist A list of records which have references to this key. This is used for fast access to signature records which are not yet checked. Note, that this is only a hint and the actual records may not anymore hold signature records for that key but that the code cares about this. 18 byte reserved Record Type 10 (hash table) -------------- Due to the fact that we use fingerprints to lookup keys, we can implement quick access by some simple hash methods, and avoid the overhead of gdbm. A property of fingerprints is that they can be used directly as hash values. (They can be considered as strong random numbers.) What we use is a dynamic multilevel architecture, which combines hashtables, record lists, and linked lists. This record is a hashtable of 256 entries; a special property is that all these records are stored consecutively to make one big table. The hash value is simple the 1st, 2nd, ... byte of the fingerprint (depending on the indirection level). When used to hash shadow directory records, a different table is used and indexed by the keyid. 1 byte value 10 1 byte reserved n u32 recnum; n depends on the record length: n = (reclen-2)/4 which yields 9 for the current record length of 40 bytes. the total number of such record which makes up the table is: m = (256+n-1) / n which is 29 for a record length of 40. To look up a key we use the first byte of the fingerprint to get the recnum from this hashtable and look up the addressed record: - If this record is another hashtable, we use 2nd byte to index this hash table and so on. - if this record is a hashlist, we walk all entries until we found one a matching one. - if this record is a key record, we compare the fingerprint and to decide whether it is the requested key; Record type 11 (hash list) -------------- see hash table for an explanation. This is also used for other purposes. 1 byte value 11 1 byte reserved 1 u32 next next hash list record n times n = (reclen-5)/5 1 u32 recnum For the current record length of 40, n is 7 Record type 254 (free record) --------------- All these records form a linked list of unused records. 1 byte value 254 1 byte reserved (0) 1 u32 next_free Packet Headers =============== GNUPG uses PGP 2 packet headers and also understands OpenPGP packet header. There is one enhancement used with the old style packet headers: CTB bits 10, the "packet-length length bits", have values listed in the following table: 00 - 1-byte packet-length field 01 - 2-byte packet-length field 10 - 4-byte packet-length field 11 - no packet length supplied, unknown packet length As indicated in this table, depending on the packet-length length bits, the remaining 1, 2, 4, or 0 bytes of the packet structure field are a "packet-length field". The packet-length field is a whole number field. The value of the packet-length field is defined to be the value of the whole number field. A value of 11 is currently used in one place: on compressed data. That is, a compressed data block currently looks like , where , binary 10 1000 11, is an indefinite-length packet. The proper interpretation is "until the end of the enclosing structure", although it should never appear outermost (where the enclosing structure is a file). + This will be changed with another version, where the new meaning of + the value 11 (see below) will also take place. + + A value of 11 for other packets enables a special length encoding, + which is used in case, where the length of the following packet can + not be determined prior to writing the packet; especially this will + be used if large amounts of data are processed in filter mode. + + It works like this: After the CTB (with a length field of 11) a + marker field is used, which gives the length of the following datablock. + This is a simple 2 byte field (MSB first) containing the amount of data + following this field, not including this length field. After this datablock + another length field follows, which gives the size of the next datablock. + A value of 0 indicates the end of the packet. The maximum size of a + data block is limited to 65534, thereby reserving a value of 0xffff for + future extensions. These length markers must be inserted into the data + stream just before writing the data out. + + This 2 byte field is large enough, because the application must buffer + this amount of data to prepend the length marker before writing it out. + Data block sizes larger than about 32k doesn't make any sense. Note + that this may also be used for compressed data streams, but we must use + another packet version to tell the application that it can not assume, + that this is the last packet. GNU extensions to the S2K algorithm =================================== S2K mode 101 is used to identify these extensions. After the hash algorithm the 3 bytes "GNU" are used to make clear that these are extensions for GNU, the next bytes gives the GNU protection mode - 1000. Defined modes are: 1001 - do not store the secret part at all 1002 - a stub to access smartcards (not used in 1.2.x) Pipemode ======== NOTE: This is deprecated and will be removed in future versions. This mode can be used to perform multiple operations with one call to gpg. It comes handy in cases where you have to verify a lot of signatures. Currently we support only detached signatures. This mode is a kludge to avoid running gpg n daemon mode and using Unix Domain Sockets to pass the data to it. There is no easy portable way to do this under Windows, so we use plain old pipes which do work well under Windows. Because there is no way to signal multiple EOFs in a pipe we have to embed control commands in the data stream: We distinguish between a data state and a control state. Initially the system is in data state but it won't accept any data. Instead it waits for transition to control state which is done by sending a single '@' character. While in control state the control command os expected and this command is just a single byte after which the system falls back to data state (but does not necesary accept data now). The simplest control command is a '@' which just inserts this character into the data stream. Here is the format we use for detached signatures: "@<" - Begin of new stream "@B" - Detached signature follows. This emits a control packet (1,'B') "@t" - Signed text follows. This emits the control packet (2, 'B') "@." - End of operation. The final control packet forces signature verification "@>" - End of stream Other Notes =========== * For packet version 3 we calculate the keyids this way: RSA := low 64 bits of n ELGAMAL := build a v3 pubkey packet (with CTB 0x99) and calculate a rmd160 hash value from it. This is used as the fingerprint and the low 64 bits are the keyid. * Revocation certificates consist only of the signature packet; "import" knows how to handle this. The rationale behind it is to keep them small. Keyserver Message Format ========================= The keyserver may be contacted by a Unix Domain socket or via TCP. The format of a request is: ==== command-tag "Content-length:" digits CRLF ======= Where command-tag is NOOP GET PUT DELETE The format of a response is: ====== "GNUPG/1.0" status-code status-text "Content-length:" digits CRLF ============ followed by bytes of data Status codes are: o 1xx: Informational - Request received, continuing process o 2xx: Success - The action was successfully received, understood, and accepted o 4xx: Client Error - The request contains bad syntax or cannot be fulfilled o 5xx: Server Error - The server failed to fulfill an apparently valid request Documentation on HKP (the http keyserver protocol): A minimalistic HTTP server on port 11371 recognizes a GET for /pks/lookup. The standard http URL encoded query parameters are this (always key=value): - op=index (like pgp -kv), op=vindex (like pgp -kvv) and op=get (like pgp -kxa) - search=. This is a list of words that must occur in the key. The words are delimited with space, points, @ and so on. The delimiters are not searched for and the order of the words doesn't matter (but see next option). - exact=on. This switch tells the hkp server to only report exact matching keys back. In this case the order and the "delimiters" are important. - fingerprint=on. Also reports the fingerprints when used with 'index' or 'vindex' The keyserver also recognizes http-POSTs to /pks/add. Use this to upload keys. A better way to do this would be a request like: /pks/lookup/?op= This can be implemented using Hurd's translator mechanism. However, I think the whole key server stuff has to be re-thought; I have some ideas and probably create a white paper.