So I am trying to understand how Monero works under the hood, and I was looking at the transaction below. (If you would like to see it in your own daemon, switch to testnet and just type `print_tx 3cf34714d411d051722ec32990bf46567c7ae3432871f75f58005cb6b5b3021e`) I would like to know what some of these fields mean. (I know that what follows might be seen as many questions, but you can view them as optional sub-questions to the main question: **How is a Monero transaction structured?**) Any insight on any of these parts, or how they are related would be greatly appreciated. For example:

1) What are the numbers inside "key_offsets"? The size of that vector seems to change according to the mixin chosen, so I assume that those numbers are a way to refer to the outputs involved in the ring signature, but what is it? I mean, clearly they aren't transaction ids,and it doesn't seem like they are block heights either.

2) What is the field "extra"?

3) Inside "rct_signatures", it says "type": 1. What is that, are there other types?

4) I assume that "mask" and "amount" are `x` and `a` in the Pedersen commitments as defined in the RingCT paper: `C(x,a) = xG + aH`. Is that correct?

5) Why is there a field called "rctsig_prunable"? Is that some information that can be discarded later?

6) What are the fields "asig", "Ci", "MGs" and "ss"?


    Found in blockchain at height 817804
    020001020005878c01c451a40.....................f910db10c69e3ff616df1e8cd73403
    {
      "version": 2, 
      "unlock_time": 0, 
      "vin": [ {
          "key": {
            "amount": 0, 
            "key_offsets": [ 17927, 10436, 804, 32, 3817
            ], 
            "k_image": "67e33ecb9fc4e697248ef57ca88aa626fe670ce1551598f9cbc1565089d43c41"
          }
        }
      ], 
      "vout": [ {
          "amount": 0, 
          "target": {
            "key": "7787bbef1a35b936e439aee4ae97cc245ba55ef35186efa3e9e86076a8fba1a6"
          }
        }, {
          "amount": 0, 
          "target": {
            "key": "f981817b20f7a866abb6a9cb29e8062a16fb15f11f0a20c0f0f296eb26e1eab1"
          }
        }
      ], 
      "extra": [ 1, 243, 27, 110, 49, 81, 52, 210, 213, 88, 152, 180, 126, 8, 156, 71, 33, 198, 169, 160, 109, 195, 45, 169, 137, 191, 32, 88, 36, 226, 210, 123, 115
      ], 
      "rct_signatures": {
        "type": 1, 
        "txnFee": 26000000000, 
        "ecdhInfo": [ {
            "mask": "d073ccb38b7e2d0e4cf0cf0ec80189bfd185e78452ae71bff7560cb80da4130e", 
            "amount": "927c6a073deb6030af17876b0e2f2a792e41ad7f8ee2b4f3200bd111818e6e0a"
          }, {
            "mask": "405c21e87c0a34452d4556617cc418820324de2dfaf3db962152ae3d37f80508", 
            "amount": "525f724a967c25be5e85292b8d822ab66e2c256af6861e758ebb500e16c9ad04"
          }], 
        "outPk": [ "e356a3285a7120d060df871a4a76d0f72550b1c323aa52252001dbff2d5a2fb2", "ca0d7844b052f6183a933dcf97a8a72acd5236d8a7f3c0b93631d5841752b504"]
      }, 
      "rctsig_prunable": {
        "rangeSigs": [ {
            "asig": "93942a5f22136543...................9b5e651c331a5f1960f", 
            "Ci": "4f08d0a8914f450723685e67....37c77d72f065bbc33157eec194be7a198bb"
          }, {
            "asig": "823405363e57560b334e2........95c9e9c9bc3726d57b4bad29a5d181bc02", 
            "Ci": "c3f62d192372296f50e916cbeef8....7b56e9962e1a660c68fed15d15c8af3"
          }], 
        "MGs": [ , 
          "ss": [ [ "f36300cd00b463281e31f32f942583800cbbe575028f0edee2a930b3aabbab08", "0acdd75b007bf52f7f7c1747450de2d99fd1a2e31c31fe6924c80bf563572f0a", ], [ "7d4c0e75b5d8aac314a8b8c5d4e54a8f2970bb92c51bdb2bbb1345ad21e3120f""2e8468a158ecf425af93c1db08f9e57be3e85fa1d33f56cef9266ad80b807d0d"], [ "19145dc851c8d79b89cc7eff289c03c583648d467a72143879db13178f5fcf05""4a0465facf45c36e89c7cac6afa0802a43e1fbd772ad7c4df821d45ef3a06c04"], [ "bbc090171e4620f7388f21e5335bff996eebcd22ac8a1b78e0e5dfe00b42600a", "d7e6ba126a9261cb33fa91deb7c179f9a0dc72b3096bc665ed8b06807b913c03", ], [ "4e5910093744557a3db315c8bc00d3422675c37fdbad4ded51ec86e8fa448c00", "b3ef06ad3142baef326ad6e70fda5e6316bb333f6519a9d893009a1d26eb5f05", ]]"c4ed83aef2fa07495da00ecdfecfc585c7f910db10c69e3ff616df1e8cd73403"]
      }
    }