summaryrefslogtreecommitdiff
path: root/api-mint.rst
blob: f6dafe956f02980b816e880a9ee3d7b6d7479548 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
=========================
The Mint RESTful JSON API
=========================

-------------------
Obtaining Mint Keys
-------------------


This API is used by wallets and merchants to obtain global information about the mint, such as online signing keys, available denominations and the fee structure.
This is typically the first call any mint client makes, as it returns information required to process all of the other interactions with the mint.  The returned
information is secured by (1) signature(s) from the mint, especially the long-term offline signing key of the mint, which clients should cache; (2) signature(s)
from auditors, and the auditor keys should be hard-coded into the wallet as they are the trust anchors for Taler; (3) possibly by using HTTPS.


.. http:get:: /keys

  Get a list of all denomination keys offered by the bank,
  as well as the bank's current online signing key.

  **Success Response: OK**

  :status 200 OK: This request should virtually always be successful.
  :resheader Content-Type: application/json
  
  .. code-block:: ts

    interface MintKeysResponse {
      // EdDSA master public key of the mint, used to sign entries in `denoms` and `signkeys`
      master_public_key: EddsaPublicKey;

      // Denomination offered by this mint.
      denoms: Denom[];

      // The date when the denomination keys were last updated.
      list_issue_date: string;

      // Auditors of the mint.
      auditors: Auditor[];

      // The mint's signing keys.
      signkeys: SignKey[];

      // compact EdDSA signature_ (binary-only) over the SHA-512 hash of the
      // concatenation of all SHA-512 hashes of the RSA denomination public keys
      // in `denoms` in the same order as they were in `denoms`.  Note that for
      // hashing, the binary format of the RSA public keys is used, and not their
      // base32_ encoding.  Wallets cannot do much with this signature by itself;
      // it is only useful when multiple clients need to establish that the mint
      // is sabotaging end-user anonymity by giving disjoint denomination keys to
      // different users.  If a mint were to do this, this signature allows the
      // clients to demonstrate to the public that the mint is dishonest.
      eddsa_sig: string;

      // Public EdDSA key of the mint that was used to generate the signature.
      // Should match one of the mint's signing keys from /keys.  It is given
      // explicitly as the client might otherwise be confused by clock skew as to
      // which signing key was used.
      eddsa_pub: string;
    }

    interface Denomination {
      // How much are coins of this denomination worth?
      value: Amount;

      // When does the denomination key become valid?
      stamp_start: Timestamp;

      // When is it no longer possible to withdraw fresh coins
      // of this denomination?
      stamp_expire_withdraw: Timestamp;

      // When is it no longer possible to deposit coins
      // of this denomination?
      stamp_expire_withdraw: Timestamp;

      // Timestamp indicating by when legal disputes relating to these coins must
      // be settled, as the mint will afterwards destroy its evidence relating to
      // transactions involving this coin.
      stamp_expire_legal: Timestamp;

      // Public (RSA) key for the denomination in base32 encoding.
      denom_pub: string;

      // Fee charged by the mint for withdrawing a coin of this denomination
      fee_withdraw: Amount;

      // Fee charged by the mint for depositing a coin of this denomination
      fee_deposit: Amount;

      // Fee charged by the mint for refreshing a coin of this denomination
      fee_refresh: Amount;

      // Signature with purpose
      // `TALER_SIGNATURE_MASTER_DENOMINATION_KEY_VALIDITY` over the expiration
      // dates, value and the key, created with the mint's master key.
      master_sig: EddsaSignature;
    }

  Fees for any of the operations can be zero, but the fields must still be present. The currency of the `fee_deposit` and `fee_refresh` must match the currency of the `value`.  Theoretically, the `fee_withdraw` could be in a different currency, but this is not currently supported by the implementation.

  A signing key in the `signkeys` list is a JSON object with the following fields:

  .. code-block:: ts

    interface SignKey {
      // The actual mint's EdDSA signing public key.
      key: EddsaPublicKey;

      // Initial validity date for the signing key.
      stamp_start: Timestamp;

      // Date when the mint will stop using the signing key, allowed to overlap
      // slightly with the next signing key's validity to allow for clock skew.
      stamp_expire: Timestamp;

      // Date when all signatures made by the signing key expire and should
      // henceforth no longer be considered valid in legal disputes.
      stamp_end: Timestamp;

      // A signature_ (binary-only) with purpose
      // `TALER_SIGNATURE_MASTER_SIGNING_KEY_VALIDITY` over the `key` and
      // `stamp_expire` by the mint master key.
      master_sig: EddsaSignature;
    }

  An entry in the `auditors` list is a JSON object with the following fields:

  .. code-block:: ts

    interface Auditor {
      // The auditor's EdDSA signing public key.
      auditor_pub: EddsaPublicKey;

      // An array of denomination keys the auditor affirms with its signature.
      // Note that the message only includes the hash of the public key, while the
      // signature is actually over the expanded information including expiration
      // times and fees.  The exact format is described below.
      denomination_keys: DenominationKey[];
    }

    interface DenominationKey {
      // hash of the public RSA key used to sign coins of the respective
      // denomination.  Note that the auditor's signature covers more than just
      // the hash, but this other information is already provided in `denoms` and
      // thus not repeated here.
      denom_pub_h: HashCode;

      // A signature_ (binary-only) with purpose
      // `TALER_SIGNATURE_AUDITOR_MINT_KEYS` over the mint's public key and the
      // denomination key information. To verify the signature, the `denom_pub_h`
      // must be resolved with the information from `denoms`
      auditor_sig: EddsaSignature;

    }

  The same auditor may appear multiple times in the array for different subsets of denomination keys, and the same denomination key hash may be listed multiple times for the same or different auditors.  The wallet or merchant just should check that the denomination keys they use are in the set for at least one of the auditors that they accept.

  .. note::

    Both the individual denominations *and* the denomination list is signed,
    allowing customers to prove that they received an inconsistent list.

-----------------------------------
Obtaining wire-transfer information
-----------------------------------

.. http:get:: /wire

  Returns a list of payment methods supported by the mint.  The idea is that wallets may use this information to instruct users on how to perform wire transfers to top up their wallets.

  **Success response: OK**

  :status 200: This request should virtually always be successful.
  :resheader Content-Type: application/json

  .. code-block:: ts

    interface WireResponse {
      // Names of supported methods (i.e. "sepa" or "test").
      // Payment method METHOD is available under /wire/METHOD.
      methods: string[];

      // the EdDSA signature_ (binary-only) with purpose
      // `TALER_SIGNATURE_MINT_PAYMENT_METHODS` signing over the hash over the
      // 0-terminated strings representing the payment methods in the same order
      // as given in methods.
      sig: EddsaSignature;

      // public EdDSA key of the mint that was used to generate the signature.
      // Should match one of the mint's signing keys from /keys.  It is given
      // explicitly as the client might otherwise be confused by clock skew as to
      // which signing key was used.
      pub: EddsaPublicKey;
    }


.. http:get:: /wire/test

  The "test" payment method is for testing the system without using
  real-world currencies or actual wire transfers.  If the mint operates
  in "test" mode, this request provides a redirect to an address where
  the user can initiate a fake wire transfer for testing.

  **Success Response: OK**

  :status 302: Redirect to the webpage where fake wire transfers can be made.

  **Failure Response: Not implemented**

  :status 501: This wire transfer method is not supported by this mint.

.. http:get:: /wire/sepa

  Provides instructions for how to transfer funds to the mint using the SEPA transfers.  Always signed using the mint's long-term offline master public key.

  **Success Response: OK**

  :status 200: This request should virtually always be successful.
  :resheader Content-Type: application/json
  :>json string receiver_name: Legal name of the mint operator who is receiving the funds
  :>json string iban: IBAN account number for the mint
  :>json string bic: BIC of the bank of the mint
  :>json base32 sig: the EdDSA signature_ (binary-only) with purpose `TALER_SIGNATURE_MINT_PAYMENT_METHOD_SEPA` signing over the hash over the 0-terminated strings representing the receiver's name, IBAN and the BIC.

  **Failure Response: Not implemented**

  :status 501: This wire transfer method is not supported by this mint.


------------------
Withdrawal
------------------

This API is used by the wallet to obtain digital coins.

When transfering money to the mint such as via SEPA transfers, the mint creates a *reserve*, which keeps the money from the customer.  The customer must specify an EdDSA reserve public key as part of the transfer, and can then withdraw digital coins using the corresponding private key.  All incoming and outgoing transactions are recorded under the corresponding public key by the mint.

  .. note::

     Eventually the mint will need to advertise a policy for how long it will keep transaction histories for inactive or even fully drained reserves.  We will therefore need some additional handler similar to `/keys` to advertise those terms of service.


.. http:get:: /reserve/status

  Request information about a reserve.

  :query reserve_pub: EdDSA reserve public key identifying the reserve.

  .. note::
    The client currently does not have to demonstrate knowledge of the private key of the reserve to make this request, which makes the reserve's public key privliged information known only to the client, their bank, and the mint.  In future, we might wish to revisit this decision to improve security, such as by having the client EdDSA-sign an ECDHE key to be used to derive a symmetric key to encrypt the response.  This would be useful if for example HTTPS were not used for communication with the mint.

  **Success Response: OK**

  :status 200 OK: The reserve was known to the mint, details about it follow in the body.
  :resheader Content-Type: application/json

  .. code-block:: ts

    interface ReserveStatus {
      // Balance left in the reserve.
      balance: Amount;

      // Transaction history for this reserve
      history: TransactionHistoryItem[];
    }

  Objects in the transaction history have the following format:

  .. code-block:: ts

    interface TransactionHistoryItem {
      // Either "WITHDRAW" or "DEPOSIT"
      type: string;

      // The amount that was withdrawn or deposited.
      amount: Amount;

      // Wiring details, only present if type is "DEPOSIT".
      wire?: any;

      // binary encoding of the transaction data as a `TALER_WithdrawRequestPS`
      // struct described in :ref:`Signatures`, only present if the `type` was
      // "WITHDRAW".  Its `purpose` should match our `type`, `amount_with_fee`,
      // should match our `amount`, and its `size` should be consistent.
      string?: details;

      // Signature over the transaction details.
      // Purpose: TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW
      signature?: EddsaSignature;


    }

  **Error Response: Unknown reserve**

  :status 404 Not Found: The withdrawal key does not belong to a reserve known to the mint.
  :resheader Content-Type: application/json
  :>json string error: the value is always "Reserve not found"
  :>json string parameter: the value is always "withdraw_pub"


.. http:post:: /reserve/withdraw

  Withdraw a coin of the specified denomination.  Note that the client should commit all of the request details, including the private key of the coin and the blinding factor, to disk *before* issuing this request, so that it can recover the information if necessary in case of transient failures, like power outage, network outage, etc.

  :reqheader Content-Type: application/json
  :<json base32 denom_pub: denomination public key (RSA), specifying the type of coin the client would like the mint to create.
  :<json base32 coin_ev: coin's blinded public key, should be (blindly) signed by the mint's denomination private key
  :<json base32 reserve_pub: public (EdDSA) key of the reserve from which the coin should be withdrawn.  The total amount deducted will be the coin's value plus the withdrawal fee as specified with the denomination information.
  :<json object reserve_sig: EdDSA signature_ (binary-only) of purpose `TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW` created with the reserves's private key

  **Success Response: OK**:

  :status 200 OK: The request was succesful.  Note that repeating exactly the same request will again yield the same response, so if the network goes down during the transaction or before the client can commit the coin signature_ to disk, the coin is not lost.
  :resheader Content-Type: application/json
  :>json base32 ev_sig: The RSA signature_ over the `coin_ev`, affirms the coin's validity after unblinding.

  **Error Response: Insufficient funds**:

  :status 402 Payment Required: The balance of the reserve is not sufficient to withdraw a coin of the indicated denomination.
  :resheader Content-Type: application/json
  :>json string error: the value is "Insufficient funds"
  :>json object balance: a JSON object with the current amount_ left in the reserve
  :>json array history: a JSON list with the history of the reserve's activity, in the same format as returned by /reserve/status.

  **Error Response: Invalid signature**:

  :status 401 Unauthorized: The signature is invalid.
  :resheader Content-Type: application/json
  :>json string error: the value is "invalid signature"
  :>json string paramter: the value is "reserve_sig"

  **Error Response: Unknown key**:

  :status 404 Not Found: The denomination key or the reserve are not known to the mint.  If the denomination key is unknown, this suggests a bug in the wallet as the wallet should have used current denomination keys from /keys.  If the reserve is unknown, the wallet should not report a hard error yet, but instead simply wait for up to a day, as the wire transaction might simply not yet have completed and might be known to the mint in the near future.  In this case, the wallet should repeat the exact same request later again using exactly the same blinded coin.
  :resheader Content-Type: application/json
  :>json string error: "unknown entity referenced"
  :>json string parameter: either "denom_pub" or "reserve_pub"


--------------------
Deposit
--------------------

Deposit operations are requested by a merchant during a transaction. For the deposit operation, the merchant has to obtain the deposit permission for a coin from their customer who owns the coin.  When depositing a coin, the merchant is credited an amount specified in the deposit permission, possibly a fraction of the total coin's value, minus the deposit fee as specified by the coin's denomination.


.. _deposit:
.. http:POST:: /deposit

  Deposit the given coin and ask the mint to transfer the given amount to the merchants bank account.  This API is used by the merchant to redeem the digital coins.  The request should contain a JSON object with the following fields:

  :reqheader Content-Type: application/json
  :<json object f: the amount_ to be deposited, can be a fraction of the coin's total value
  :<json object `wire`: the merchant's account details. This must be a JSON object whose format must correspond to one of the supported wire transfer formats of the mint.  See :ref:`wireformats`
  :<json base32 H_wire: SHA-512 hash of the merchant's payment details from `wire`.  Although strictly speaking redundant, this helps detect inconsistencies.
  :<json base32 H_contract: SHA-512 hash of the contact of the merchant with the customer.  Further details are never disclosed to the mint.
  :<json base32 coin_pub: coin's public key, both ECDHE and EdDSA.
  :<json base32 denom_pub: denomination RSA key with which the coin is signed
  :<json base32 ub_sig: mint's unblinded RSA signature_ of the coin
  :<json date timestamp: timestamp when the contract was finalized, must match approximately the current time of the mint
  :<json date edate: indicative time by which the mint undertakes to transfer the funds to the merchant, in case of successful payment.
  :<json int transaction_id: 64-bit transaction id for the transaction between merchant and customer
  :<json base32 merchant_pub: the EdDSA public key of the merchant, so that the client can identify the merchant for refund requests.
  :<json date refund_deadline: date until which the merchant can issue a refund to the customer via the mint, possibly zero if refunds are not allowed.
  :<json base32 coin_sig: the EdDSA signature_ (binary-only) made with purpose `TALER_SIGNATURE_WALLET_COIN_DEPOSIT` made by the customer with the coin's private key.

  The deposit operation succeeds if the coin is valid for making a deposit and has enough residual value that has not already been deposited or melted.

  **Success response: OK**

  :status 200: the operation succeeded, the mint confirms that no double-spending took place.
  :resheader Content-Type: application/json
  :>json string status: the string constant `DEPOSIT_OK`
  :>json base32 sig: the EdDSA signature_ (binary-only) with purpose `TALER_SIGNATURE_MINT_CONFIRM_DEPOSIT` using a current signing key of the mint affirming the successful deposit and that the mint will transfer the funds after the refund deadline, or as soon as possible if the refund deadline is zero.
  :>json base32 pub: public EdDSA key of the mint that was used to generate the signature.  Should match one of the mint's signing keys from /keys.  It is given explicitly as the client might otherwise be confused by clock skew as to which signing key was used.

  **Failure response: Double spending**

  :status 403: the deposit operation has failed because the coin has insufficient residual value; the request should not be repeated again with this coin.
  :resheader Content-Type: application/json
  :>json string error: the string "insufficient funds"
  :>json object history: a JSON array with the transaction history for the coin

  The transaction history contains entries of the following format:

  :>jsonarr string type: either "deposit" or "melt"
  :>jsonarr object amount: the total amount_ of the coin's value absorbed by this transaction
  :>jsonarr string details: base32_ binary encoding of the transaction data as a `TALER_DepositRequestPS` or `TALER_RefreshMeltCoinAffirmationPS` struct described in :ref:`Signatures`.  Its `purpose` should match our `type`, `amount_with_fee`, should match our `amount`, and its `size` should be consistent.
  :>jsonarr object signature: the EdDSA signature_ (binary-only) made with purpose `TALER_SIGNATURE_WALLET_COIN_DEPOSIT` or `TALER_SIGNATURE_WALLET_COIN_MELT` over the transaction's details.

  **Error Response: Invalid signature**:

  :status 401 Unauthorized: One of the signatures is invalid.
  :resheader Content-Type: application/json
  :>json string error: the value is "invalid signature"
  :>json string paramter: the value is "coin_sig" or "ub_sig", depending on which signature was deemed invalid by the mint

  **Failure response: Unknown denomination key**

  :status 404: the mint does not recognize the denomination key as belonging to the mint, or it has expired
  :resheader Content-Type: application/json
  :>json string error: the value is "unknown entity referenced"
  :>json string paramter: the value is "denom_pub"

  **Failure response: Unsupported or invalid wire format**

  :status 404: the mint does not recognize the wire format (unknown type or format check fails)
  :resheader Content-Type: application/json
  :>json string error: the value is "unknown entity referenced"
  :>json string paramter: the value is "wire"



------------------
Refreshing
------------------

Refreshing creates `n` new coins from `m` old coins, where the sum of denominations of the new coins must be smaller than the sum of the old coins' denominations plus melting (refresh) and withdrawal fees charged by the mint.  The refreshing API can be used by wallets to melt partially spent coins, making transactions with the freshly minted coins unlinkabe to previous transactions by anyone except the wallet itself.

However, the new coins are linkable from the private keys of all old coins using the /refresh/link request.  While /refresh/link must be implemented by the mint to achieve taxability, wallets do not really ever need that part of the API during normal operation.

.. _refresh:
.. http:post:: /refresh/melt

  "Melts" coins.  Invalidates the coins and prepares for minting of fresh coins.  Taler uses a global parameter `kappa` for the cut-and-choose component of the protocol, for which this request is the commitment.  Thus, various arguments are given `kappa`-times in this step.  At present `kappa` is always 3.

  The request body must contain a JSON object with the following fields:

  :<json array new_denoms: List of `n` new denominations to order. Each entry must be a base32_ encoded RSA public key corresponding to the coin to be minted.
  :<json array melt_coins: List of `m` coins to melt.
  :<json array coin_evs: For each of the `n` new coins, `kappa` coin blanks (2D array)
  :<json array transfer_pubs: For each of the `m` old coins, `kappa` transfer public keys (2D-array of ephemeral ECDHE keys)
  :<json array secret_encs: For each of the `m` old coins, `kappa` link encryptions with an ECDHE-encrypted SHA-512 hash code.  The ECDHE encryption is done using the private key of the respective old coin and the corresponding transfer public key.  Note that the SHA-512 hash code must be the same across all coins, but different across all of the `kappa` dimensions.  Given the private key of a single old coin, it is thus possible to decrypt the respective `secret_encs` and obtain the SHA-512 hash that was used to symetrically encrypt the `link_encs` of all of the new coins.
  :<json array link_encs: For each of the `n` new coins, `kappa` symmetricly encrypted tuples consisting of the EdDSA/ECDHE-private key of the new coin and the corresponding blinding factor, encrypted using the corresponding SHA-512 hash that is encrypted in `secret_encs`.

  For details about the HKDF used to derive the symmetric encryption keys from ECDHE and the symmetric encryption (AES+Twofish) used, please refer to the implementation in `libtalerutil`. The `melt_coins` field is a list of JSON objects with the following fields:

  :<jsonarr string coin_pub: Coin public key (uniquely identifies the coin)
  :<jsonarr string denom_pub: Denomination public key (allows the mint to determine total coin value)
  :<jsonarr string denom_sig: Signature_ over the coin public key by the denomination
  :<jsonarr string confirm_sig: Signature_ by the coin over the session public key
     key
  :<jsonarr object value_with_fee: Amount_ of the value of the coin that should be melted as part of this refresh operation, including melting fee.

  Errors such as failing to do proper arithmetic when it comes to calculating the total of the coin values and fees are simply reported as bad requests.  This includes issues such as melting the same coin twice in the same session, which is simply not allowed.  However, theoretically it is possible to melt a coin twice, as long as the `value_with_fee` of the two melting operations is not larger than the total remaining value of the coin before the melting operations. Nevertheless, this is not really useful.

  **Success Response: OK**

  :status 200 OK: The request was succesful. The response body contains a JSON object with the following fields:
  :resheader Content-Type: application/json
  :>json int noreveal_index: Which of the `kappa` indices does the client not have to reveal.
  :>json base32 mint_sig: binary-only Signature_ for purpose `TALER_SIGNATURE_MINT_CONFIRM_MELT` whereby the mint affirms the successful melt and confirming the `noreveal_index`
  :>json base32 mint_pub: public EdDSA key of the mint that was used to generate the signature.  Should match one of the mint's signing keys from /keys.  Again given explicitly as the client might otherwise be confused by clock skew as to which signing key was used.

  **Error Response: Invalid signature**:

  :status 401 Unauthorized: One of the signatures is invalid.
  :resheader Content-Type: application/json
  :>json string error: the value is "invalid signature"
  :>json string paramter: the value is "confirm_sig" or "denom_sig", depending on which signature was deemed invalid by the mint

  **Error Response: Precondition failed**:

  :status 403 Forbidden: The operation is not allowed as at least one of the coins has insufficient funds.
  :resheader Content-Type: application/json
  :>json string error: the value is "insufficient funds"
  :>json base32 coin_pub: public key of a melted coin that had insufficient funds
  :>json amount original_value: original total value of the coin
  :>json amount residual_value: remaining value of the coin
  :>json amount requested_value: amount of the coin's value that was to be melted
  :>json array history: the transaction list of the respective coin that failed to have sufficient funds left.  The format is the same as for insufficient fund reports during /deposit.  Note that only the transaction history for one bogus coin is given, even if multiple coins would have failed the check.

  **Failure response: Unknown denomination key**

  :status 404: the mint does not recognize the denomination key as belonging to the mint, or it has expired
  :resheader Content-Type: application/json
  :>json string error: the value is "unknown entity referenced"
  :>json string paramter: the value is "denom_pub"

.. http:post:: /refresh/reveal

  Reveal previously commited values to the mint, except for the values corresponding to the `noreveal_index` returned by the /mint/melt step.  Request body contains a JSON object with the following fields:

  :<json base32 session_hash: Hash over most of the arguments to the /mint/melt step.  Used to identify the corresponding melt operation.  For details on which elements must be hashed in which order, please consult the mint code itself.
  :<json array transfer_privs: 2D array of `kappa - 1` times number of melted coins ECDHE transfer private keys.  The mint will use those to decrypt the transfer secrets, check that they match across all coins, and then decrypt the private keys of the coins to be generated and check all this against the commitments.

  **Success Response: OK**

  :status 200 OK: The transfer private keys matched the commitment and the original request was well-formed.  The mint responds with a JSON of the following type:
  :resheader Content-Type: application/json
  :>json array ev_sigs: List of the mint's blinded RSA signatures on the new coins.  Each element in the array is another JSON object which contains the signature in the "ev_sig" field.

  **Failure Response: Conflict**

  :status 409 Conflict: There is a problem between the original commitment and the revealed private keys.  The returned information is proof of the missmatch, and therefore rather verbose, as it includes most of the original /refresh/melt request, but of course expected to be primarily used for diagnostics.
  :resheader Content-Type: application/json
  :>json string error: the value is "commitment violation"
  :>json int offset: offset of in the array of `kappa` commitments where the error was detected
  :>json int index: index of in the with respect to the melted coin where the error was detected
  :>json string object: name of the entity that failed the check (i.e. "transfer key")
  :>json array oldcoin_infos: array with information for each melted coin
  :>json array newcoin_infos: array with RSA denomination public keys of the coins the original refresh request asked to be minted
  :>json array link_infos: 2D array with `kappa` entries in the first dimension and the same length as the `oldcoin_infos` in the 2nd dimension containing as elements objects with the linkage information
  :>json array commit_infos: 2D array with `kappa` entries in the first dimension and the same length as `newcoin_infos` in the 2nd dimension containing as elements objects with the commitment information

  The linkage information from `link_infos` consists of:

  :>jsonarr base32 transfer_pub: the transfer ECDHE public key
  :>jsonarr base32 shared_secret_enc: the encrypted shared secret

  The commit information from `commit_infos` consists of:

  :>jsonarr base32 coin_ev: the coin envelope (information to sign blindly)
  :>jsonarr base32 coin_priv_enc: the encrypted private key of the coin
  :>jsonarr base32 blinding_key_enc: the encrypted blinding key

.. http:get:: /refresh/link

  Link the old public key of a melted coin to the coin(s) that were minted during the refresh operation.

  :query coin_pub: melted coin's public key

  **Success Response**

  :status 200 OK: All commitments were revealed successfully.  The mint returns an array, typically consisting of only one element, in which each each element contains information about a melting session that the coin was used in.

  :>jsonarr base32 transfer_pub: transfer ECDHE public key corresponding to the `coin_pub`, used to decrypt the `secret_enc` in combination with the private key of `coin_pub`.
  :>jsonarr base32 secret_enc: ECDHE-encrypted link secret that, once decrypted, can be used to decrypt/unblind the `new_coins`.
  :>jsonarr array new_coins: array with (encrypted/blinded) information for each of the coins minted in the refresh operation.

  The `new_coins` array contains the following fields for each element:

  :>jsonarr base32 link_enc: Encrypted private key and blinding factor information of the fresh coin
  :>jsonarr base32 denom_pub: RSA public key of the minted coin.
  :>jsonarr base32 ev_sig: Mint's blinded signature over the minted coin.

  **Error Response: Unknown key**:

  :status 404 Not Found: The mint has no linkage data for the given public key, as the coin has not yet been involved in a refresh operation.
  :resheader Content-Type: application/json
  :>json string error: "unknown entity referenced"
  :>json string parameter: will be "coin_pub"



-----------------------
Tracking wire transfers
-----------------------

This API is used by merchants that need to find out which wire
transfers (from the mint to the merchant) correspond to which deposit
operations.  Typically, a merchant will receive a wire transfer with a
**wire transfer identifier** and want to know the set of deposit
operations that correspond to this wire transfer.  This is the
preferred query that merchants should make for each wire transfer they
receive.  If a merchant needs to investigate a specific deposit
operation (i.e. because it seems that it was not paid), then the
merchant can also request the wire transfer identifier for a deposit
operation.

Sufficient information is returned to verify that the coin signatures
are correct. This also allows governments to use this API when doing
a tax audit on merchants.

Naturally, the returned information may be sensitive for the merchant.
We do not require the merchant to sign the request, as the same requests
may also be performed by the government auditing a merchant.
However, wire transfer identifiers should have sufficient entropy to
ensure that obtaining a successful reply by brute-force is not practical.
Nevertheless, the merchant should protect the wire transfer identifiers
from his bank statements against unauthorized access, least his income
situation is revealed to an adversary. (This is not a major issue, as
an adversary that has access to the line-items of bank statements can
typically also view the balance.)

  .. note::

     Wire transfer tracking is currently not implemented (#3888).


.. http:get:: /wire/deposits

  Provides deposits associated with a given wire transfer.

  :query wtid: wire transfer identifier identifying the wire transfer (a base32-encoded value)

  **Success Response: OK**

  :status 200 OK: The wire transfer is known to the mint, details about it follow in the body.
  :resheader Content-Type: application/json
  :>json object total: Total amount_ transferred.
  :>json base32 H_wire: hash of the wire details (identical for all deposits)
  :>json base32 merchant_pub: public key of the merchant (identical for all deposits)
  :>json object deposits: JSON array with **deposit details**.

  Objects in the `deposits` array have the following format:

  :>jsonarr object deposit_value: the total amount_ the original deposit was worth
  :>jsonarr object deposit_fee: applicable fees for the deposit
  :>jsonarr base32 H_contract: SHA-512 hash of the contact of the merchant with the customer.
  :>jsonarr int transaction_id: 64-bit transaction id for the transaction between merchant and customer
  :>jsonarr base32 coin_pub: coin's public key, both ECDHE and EdDSA.


  **Error Response: Unknown wire transfer identifier**

  :status 404 Not Found: The wire transfer identifier is unknown to the mint.
  :resheader Content-Type: application/json
  :>json string error: the value is always "Wire transfer identifier not found"
  :>json string parameter: the value is always "wtid"


.. http:post:: /deposit/wtid

  Provide the wire transfer identifier associated with an (existing) deposit operation.

  :reqheader Content-Type: application/json
  :<json base32 H_wire: SHA-512 hash of the merchant's payment details.
  :<json base32 H_contract: SHA-512 hash of the contact of the merchant with the customer.
  :<json base32 coin_pub: coin's public key, both ECDHE and EdDSA.
  :<json int transaction_id: 64-bit transaction id for the transaction between merchant and customer
  :<json base32 merchant_pub: the EdDSA public key of the merchant, so that the client can identify the merchant for refund requests.
  :<json base32 merchant_sig: the EdDSA signature of the merchant made with purpose `TALER_SIGNATURE_MERCHANT_DEPOSIT_WTID` , affirming that it is really the merchant who requires obtaining the wire transfer identifier.

  **Success Response: OK**

  :status 200 OK: The deposit has been executed by the mint and we have a wire transfer identifier.
  :resheader Content-Type: application/json
  :>json base32 wtid: wire transfer identifier of the deposit.
  :>json date execution_time: when was the wire transfer given to the bank.
  :>json base32 mint_sig: binary-only Signature_ for purpose `TALER_SIGNATURE_MINT_CONFIRM_WIRE` whereby the mint affirms the successful wire transfer.
  :>json base32 mint_pub: public EdDSA key of the mint that was used to generate the signature.  Should match one of the mint's signing keys from /keys.  Again given explicitly as the client might otherwise be confused by clock skew as to which signing key was used.

  **Error Response: Wire transfer not yet executed**

  :status 202 Accepted: The deposit request has been accepted for processing, but was not yet executed.  Hence the mint does not yet have a wire transfer identifier.  The merchant should come back later and ask again.
  :resheader Content-Type: application/json
  :>json date execution_time: time by which the mint currently thinks the deposit will be executed.

  **Error Response: Invalid signature**:

  :status 401 Unauthorized: The signature is invalid.
  :resheader Content-Type: application/json
  :>json string error: the value is "invalid signature"
  :>json string paramter: the value is "merchant_sig"

  **Error Response: Unknown wire transfer identifier**

  :status 404 Not Found: The deposit operation is unknown to the mint
  :resheader Content-Type: application/json
  :>json string error: the value is always "Deposit unknown"





-------
Refunds
-------

  .. note::

     Refunds are currently not implemented (#3641), this documentation is thus rather preliminary and subject to change.

.. _refund:
.. http:POST:: /refund

  Undo deposit of the given coin, restoring its value.  The request
  should contain a JSON object with the following fields:

  :>json obj retract_perm: If the coin was claimed as a refund, this field should contain the retract permission obtained from the merchant, otherwise it should not be present.  For details about the object type, see :ref:`Merchant API:retract<retract>`.
  :>json string retract_value: Value returned due to the retraction.



------------------------------
Administrative API: Key update
------------------------------

  .. note::

     This is not yet implemented (no bug number yet, as we are not sure we will implement this; for now, adding new files to the directory and sending a signal to the mint process seems to work fine).

New denomination and signing keys can be uploaded to the mint via the
HTTP interface.  It is, of course, only possible to upload keys signed
by the mint's master key.  Furthermore, this API should probably only
be used via loopback, as we want to protect the private keys from
interception.

.. http:POST:: /admin/add/denomination_key

  Upload a new denomination key.

  :>json object denom_info: Public part of the denomination key
  :>json base32 denom_priv: Private RSA key

.. http:POST:: /admin/add/sign_key

  Upload a new signing key.

  :>json object sign_info: Public part of the signing key
  :>json base32 sign_priv: Private EdDSA key

.. _add-incoming:

-------------------------------------
Administrative API: Bank transactions
-------------------------------------

.. http:POST:: /admin/add/incoming

  Notify mint of an incoming transaction to fill a reserve.

  :>json base32 reserve_pub: Reserve public key
  :>json object amount: Amount transferred to the reserve
  :>json date execution_date: When was the transaction executed
  :>json object wire: Wire details

  **Success response**

  :status 200: the operation succeeded

  The mint responds with a JSON object containing the following fields:

  :>json string status: The string constant `NEW` or `DUP` to indicate
     whether the transaction was truly added to the DB
     or whether it already existed in the DB

  **Failure response**

  :status 403: the client is not permitted to add incoming transactions. The request may be disallowed by the configuration in general or restricted to certain IP addresses (i.e. loopback-only).

  The mint responds with a JSON object containing the following fields:

  :>json string error: the error message, such as `permission denied`
  :>json string hint: hint as to why permission was denied


.. http:POST:: /admin/add/outgoing

  Notify mint about the completion of an outgoing transaction satisfying a /deposit request.  In the future, this will allow merchants to obtain details about the /deposit requests they send to the mint.

  .. note::

     This is not yet implemented (no bug number yet either).

  :>json base32 coin_pub: Coin public key
  :>json object amount: Amount transferred to the merchant
  :>json string transaction: Transaction identifier in the wire details
  :>json base32 wire: Wire transaction details, as originally specified by the merchant


  **Success response**

  :status 200: the operation succeeded

  The mint responds with a JSON object containing the following fields:

  :>json string status: The string constant `NEW` or `DUP` to indicate
     whether the transaction was truly added to the DB
     or whether it already existed in the DB

  **Failure response**

  :status 403: the client is not permitted to add outgoing transactions

  The mint responds with a JSON object containing the following fields:

  :>json string error: the error message (`permission denied`)
  :>json string hint: hint as to why permission was denied

------------
The Test API
------------

The test API is not there to test the mint, but to allow
clients of the mint (merchant and wallet implementations)
to test if their implemenation of the cryptography is
binary-compatible with the implementation of the mint.

.. http:POST:: /test/base32

  Test hashing and Crockford base32_ encoding.

  :reqheader Content-Type: application/json
  :<json base32 input: some base32_-encoded value
  :status 200: the operation succeeded
  :resheader Content-Type: application/json
  :>json base32 output: the base32_-encoded hash of the input value

.. http:POST:: /test/encrypt

  Test symmetric encryption.

  :reqheader Content-Type: application/json
  :<json base32 input: some base32_-encoded value
  :<json base32 key_hash: some base32_-encoded hash that is used to derive the symmetric key and initialization vector for the encryption using the HKDF with "skey" and "iv" as the salt.
  :status 200: the operation succeeded
  :resheader Content-Type: application/json
  :>json base32 output: the encrypted value

.. http:POST:: /test/hkdf

  Test Hash Key Deriviation Function.

  :reqheader Content-Type: application/json
  :<json base32 input: some base32_-encoded value
  :status 200: the operation succeeded
  :resheader Content-Type: application/json
  :>json base32 output: the HKDF of the input using "salty" as salt

.. http:POST:: /test/ecdhe

  Test ECDHE.

  :reqheader Content-Type: application/json
  :<json base32 ecdhe_pub: ECDHE public key
  :<json base32 ecdhe_priv: ECDHE private key
  :status 200: the operation succeeded
  :resheader Content-Type: application/json
  :>json base32 ecdh_hash: ECDH result from the two keys

.. http:POST:: /test/eddsa

  Test EdDSA.

  :reqheader Content-Type: application/json
  :<json base32 eddsa_pub: EdDSA public key
  :<json base32 eddsa_sig: EdDSA signature using purpose TALER_SIGNATURE_CLIENT_TEST_EDDSA. Note: the signed payload must be empty, we sign just the purpose here.
  :status 200: the signature was valid
  :resheader Content-Type: application/json
  :>json base32 eddsa_pub: Another EdDSA public key
  :>json base32 eddsa_sig: EdDSA signature using purpose TALER_SIGNATURE_MINT_TEST_EDDSA

.. http:GET:: /test/rsa/get

  Obtain the RSA public key used for signing in /test/rsa/sign.

  :status 200: operation was successful
  :resheader Content-Type: application/json
  :>json base32 rsa_pub: The RSA public key the client should use when blinding a value for the /test/rsa/sign API.

.. http:POST:: /test/rsa/sign

  Test RSA blind signatures.

  :reqheader Content-Type: application/json
  :<json base32 blind_ev: Blinded value to sign.
  :status 200: operation was successful
  :resheader Content-Type: application/json
  :>json base32 rsa_blind_sig: Blind RSA signature over the `blind_ev` using the private key corresponding to the RSA public key returned by /test/rsa/get.


.. http:POST:: /test/transfer

  Test Transfer decryption.

  :reqheader Content-Type: application/json
  :<json base32 secret_enc: Encrypted transfer secret
  :<json base32 trans_priv: Private transfer key
  :<json base32 coin_pub: Public key of a coin
  :status 200: the operation succeeded
  :resheader Content-Type: application/json
  :>json base32 secret: Decrypted transfer secret