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cristalolegcristaloleg
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Implement v4.local (#11)
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‎testdata/v4.json

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{
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"name": "PASETO v4 Test Vectors",
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"tests": [
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{
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"name": "4-E-1",
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"expect-fail": false,
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"nonce": "0000000000000000000000000000000000000000000000000000000000000000",
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"token": "v4.local.AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAr68PS4AXe7If_ZgesdkUMvSwscFlAl1pk5HC0e8kApeaqMfGo_7OpBnwJOAbY9V7WU6abu74MmcUE8YWAiaArVI8XJ5hOb_4v9RmDkneN0S92dx0OW4pgy7omxgf3S8c3LlQg",
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"payload": "{\"data\":\"this is a secret message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-2",
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"expect-fail": false,
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"nonce": "0000000000000000000000000000000000000000000000000000000000000000",
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"token": "v4.local.AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAr68PS4AXe7If_ZgesdkUMvS2csCgglvpk5HC0e8kApeaqMfGo_7OpBnwJOAbY9V7WU6abu74MmcUE8YWAiaArVI8XIemu9chy3WVKvRBfg6t8wwYHK0ArLxxfZP73W_vfwt5A",
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"payload": "{\"data\":\"this is a hidden message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-3",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WkwMsYXw6FSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t6-tyebyWG6Ov7kKvBdkrrAJ837lKP3iDag2hzUPHuMKA",
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"payload": "{\"data\":\"this is a secret message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-4",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WiA8rd3wgFSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t4gt6TiLm55vIH8c_lGxxZpE3AWlH4WTR0v45nsWoU3gQ",
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"payload": "{\"data\":\"this is a hidden message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-5",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WkwMsYXw6FSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t4x-RMNXtQNbz7FvFZ_G-lFpk5RG3EOrwDL6CgDqcerSQ.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
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"payload": "{\"data\":\"this is a secret message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-6",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WiA8rd3wgFSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t6pWSA5HX2wjb3P-xLQg5K5feUCX4P2fpVK3ZLWFbMSxQ.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
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"payload": "{\"data\":\"this is a hidden message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
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"implicit-assertion": ""
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},
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{
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"name": "4-E-7",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WkwMsYXw6FSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t40KCCWLA7GYL9KFHzKlwY9_RnIfRrMQpueydLEAZGGcA.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
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"payload": "{\"data\":\"this is a secret message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
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"implicit-assertion": "{\"test-vector\":\"4-E-7\"}"
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},
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{
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"name": "4-E-8",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WiA8rd3wgFSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t5uvqQbMGlLLNYBc7A6_x7oqnpUK5WLvj24eE4DVPDZjw.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
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"payload": "{\"data\":\"this is a hidden message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
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"implicit-assertion": "{\"test-vector\":\"4-E-8\"}"
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},
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{
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"name": "4-E-9",
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"expect-fail": false,
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"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
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"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
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"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WiA8rd3wgFSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t6tybdlmnMwcDMw0YxA_gFSE_IUWl78aMtOepFYSWYfQA.YXJiaXRyYXJ5LXN0cmluZy10aGF0LWlzbid0LWpzb24",
90+
"payload": "{\"data\":\"this is a hidden message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "arbitrary-string-that-isn't-json",
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"implicit-assertion": "{\"test-vector\":\"4-E-9\"}"
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},
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{
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"name": "4-S-1",
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"expect-fail": false,
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"public-key": "1eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
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"secret-key": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a37741eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
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"secret-key-seed": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a3774",
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"secret-key-pem": "-----BEGIN PRIVATE KEY-----\nMC4CAQAwBQYDK2VwBCIEILTL+0PfTOIQcn2VPkpxMwf6Gbt9n4UEFDjZ4RuUKjd0\n-----END PRIVATE KEY-----",
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"public-key-pem": "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEAHrnbu7wEfAP9cGBOAHHwmH4Wsot1ciXBHwBBXQ4gsaI=\n-----END PUBLIC KEY-----",
102+
"token": "v4.public.eyJkYXRhIjoidGhpcyBpcyBhIHNpZ25lZCBtZXNzYWdlIiwiZXhwIjoiMjAyMi0wMS0wMVQwMDowMDowMCswMDowMCJ9bg_XBBzds8lTZShVlwwKSgeKpLT3yukTw6JUz3W4h_ExsQV-P0V54zemZDcAxFaSeef1QlXEFtkqxT1ciiQEDA",
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"payload": "{\"data\":\"this is a signed message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
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"footer": "",
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"implicit-assertion": ""
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},
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{
108+
"name": "4-S-2",
109+
"expect-fail": false,
110+
"public-key": "1eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
111+
"secret-key": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a37741eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
112+
"secret-key-seed": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a3774",
113+
"secret-key-pem": "-----BEGIN PRIVATE KEY-----\nMC4CAQAwBQYDK2VwBCIEILTL+0PfTOIQcn2VPkpxMwf6Gbt9n4UEFDjZ4RuUKjd0\n-----END PRIVATE KEY-----",
114+
"public-key-pem": "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEAHrnbu7wEfAP9cGBOAHHwmH4Wsot1ciXBHwBBXQ4gsaI=\n-----END PUBLIC KEY-----",
115+
"token": "v4.public.eyJkYXRhIjoidGhpcyBpcyBhIHNpZ25lZCBtZXNzYWdlIiwiZXhwIjoiMjAyMi0wMS0wMVQwMDowMDowMCswMDowMCJ9v3Jt8mx_TdM2ceTGoqwrh4yDFn0XsHvvV_D0DtwQxVrJEBMl0F2caAdgnpKlt4p7xBnx1HcO-SPo8FPp214HDw.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
116+
"payload": "{\"data\":\"this is a signed message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
117+
"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
118+
"implicit-assertion": ""
119+
},
120+
{
121+
"name": "4-S-3",
122+
"expect-fail": false,
123+
"public-key": "1eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
124+
"secret-key": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a37741eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
125+
"secret-key-seed": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a3774",
126+
"secret-key-pem": "-----BEGIN PRIVATE KEY-----\nMC4CAQAwBQYDK2VwBCIEILTL+0PfTOIQcn2VPkpxMwf6Gbt9n4UEFDjZ4RuUKjd0\n-----END PRIVATE KEY-----",
127+
"public-key-pem": "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEAHrnbu7wEfAP9cGBOAHHwmH4Wsot1ciXBHwBBXQ4gsaI=\n-----END PUBLIC KEY-----",
128+
"token": "v4.public.eyJkYXRhIjoidGhpcyBpcyBhIHNpZ25lZCBtZXNzYWdlIiwiZXhwIjoiMjAyMi0wMS0wMVQwMDowMDowMCswMDowMCJ9NPWciuD3d0o5eXJXG5pJy-DiVEoyPYWs1YSTwWHNJq6DZD3je5gf-0M4JR9ipdUSJbIovzmBECeaWmaqcaP0DQ.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
129+
"payload": "{\"data\":\"this is a signed message\",\"exp\":\"2022-01-01T00:00:00+00:00\"}",
130+
"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
131+
"implicit-assertion": "{\"test-vector\":\"4-S-3\"}"
132+
},
133+
{
134+
"name": "4-F-1",
135+
"expect-fail": true,
136+
"public-key": "1eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
137+
"secret-key": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a37741eb9dbbbbc047c03fd70604e0071f0987e16b28b757225c11f00415d0e20b1a2",
138+
"secret-key-seed": "b4cbfb43df4ce210727d953e4a713307fa19bb7d9f85041438d9e11b942a3774",
139+
"secret-key-pem": "-----BEGIN PRIVATE KEY-----\nMC4CAQAwBQYDK2VwBCIEILTL+0PfTOIQcn2VPkpxMwf6Gbt9n4UEFDjZ4RuUKjd0\n-----END PRIVATE KEY-----",
140+
"public-key-pem": "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEAHrnbu7wEfAP9cGBOAHHwmH4Wsot1ciXBHwBBXQ4gsaI=\n-----END PUBLIC KEY-----",
141+
"token": "v4.local.vngXfCISbnKgiP6VWGuOSlYrFYU300fy9ijW33rznDYgxHNPwWluAY2Bgb0z54CUs6aYYkIJ-bOOOmJHPuX_34Agt_IPlNdGDpRdGNnBz2MpWJvB3cttheEc1uyCEYltj7wBQQYX.YXJiaXRyYXJ5LXN0cmluZy10aGF0LWlzbid0LWpzb24",
142+
"payload": null,
143+
"footer": "arbitrary-string-that-isn't-json",
144+
"implicit-assertion": "{\"test-vector\":\"4-F-1\"}"
145+
},
146+
{
147+
"name": "4-F-2",
148+
"expect-fail": true,
149+
"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
150+
"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
151+
"token": "v4.public.eyJpbnZhbGlkIjoidGhpcyBzaG91bGQgbmV2ZXIgZGVjb2RlIn22Sp4gjCaUw0c7EH84ZSm_jN_Qr41MrgLNu5LIBCzUr1pn3Z-Wukg9h3ceplWigpoHaTLcwxj0NsI1vjTh67YB.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
152+
"payload": null,
153+
"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
154+
"implicit-assertion": "{\"test-vector\":\"4-F-2\"}"
155+
},
156+
{
157+
"name": "4-F-3",
158+
"expect-fail": true,
159+
"nonce": "26f7553354482a1d91d4784627854b8da6b8042a7966523c2b404e8dbbe7f7f2",
160+
"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
161+
"token": "v3.local.23e_2PiqpQBPvRFKzB0zHhjmxK3sKo2grFZRRLM-U7L0a8uHxuF9RlVz3Ic6WmdUUWTxCaYycwWV1yM8gKbZB2JhygDMKvHQ7eBf8GtF0r3K0Q_gF1PXOxcOgztak1eD1dPe9rLVMSgR0nHJXeIGYVuVrVoLWQ.YXJiaXRyYXJ5LXN0cmluZy10aGF0LWlzbid0LWpzb24",
162+
"payload": null,
163+
"footer": "arbitrary-string-that-isn't-json",
164+
"implicit-assertion": "{\"test-vector\":\"4-F-3\"}"
165+
},
166+
{
167+
"name": "4-F-4",
168+
"expect-fail": true,
169+
"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
170+
"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
171+
"token": "v4.local.AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAr68PS4AXe7If_ZgesdkUMvSwscFlAl1pk5HC0e8kApeaqMfGo_7OpBnwJOAbY9V7WU6abu74MmcUE8YWAiaArVI8XJ5hOb_4v9RmDkneN0S92dx0OW4pgy7omxgf3S8c3LlQh",
172+
"payload": null,
173+
"footer": "",
174+
"implicit-assertion": ""
175+
},
176+
{
177+
"name": "4-F-5",
178+
"expect-fail": true,
179+
"nonce": "df654812bac492663825520ba2f6e67cf5ca5bdc13d4e7507a98cc4c2fcc3ad8",
180+
"key": "707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f",
181+
"token": "v4.local.32VIErrEkmY4JVILovbmfPXKW9wT1OdQepjMTC_MOtjA4kiqw7_tcaOM5GNEcnTxl60WkwMsYXw6FSNb_UdJPXjpzm0KW9ojM5f4O2mRvE2IcweP-PRdoHjd5-RHCiExR1IK6t4x-RMNXtQNbz7FvFZ_G-lFpk5RG3EOrwDL6CgDqcerSQ==.eyJraWQiOiJ6VmhNaVBCUDlmUmYyc25FY1Q3Z0ZUaW9lQTlDT2NOeTlEZmdMMVc2MGhhTiJ9",
182+
"payload": null,
183+
"footer": "{\"kid\":\"zVhMiPBP9fRf2snEcT7gFTioeA9COcNy9DfgL1W60haN\"}",
184+
"implicit-assertion": ""
185+
}
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]
187+
}

‎v4loc.go

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1+
package paseto
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import (
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"crypto/hmac"
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"crypto/rand"
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"errors"
7+
"fmt"
8+
"io"
9+
"strings"
10+
11+
"golang.org/x/crypto/blake2b"
12+
"golang.org/x/crypto/chacha20"
13+
)
14+
15+
const (
16+
v4locHeader = "v4.local."
17+
v4locKey = 32
18+
v4locNonce = 32
19+
v4locMac = 32
20+
v4locKDF = 32
21+
)
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func V4Encrypt(key []byte, payload, footer any, implicit string, randBytes []byte) (string, error) {
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payloadBytes, err := toBytes(payload)
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if err != nil {
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return "", fmt.Errorf("encode payload: %w", err)
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}
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footerBytes, err := toBytes(footer)
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if err != nil {
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return "", fmt.Errorf("encode footer: %w", err)
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}
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if randBytes == nil {
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randBytes = make([]byte, v4locNonce)
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if _, err := io.ReadFull(rand.Reader, randBytes); err != nil {
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return "", fmt.Errorf("read from crypto/rand.Reader: %w", err)
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}
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}
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// step 0.
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m := payloadBytes
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k := key
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f := footerBytes
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i := []byte(implicit)
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// step 1.
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if !constTimeEq(int32(len(k)), v4locKey) {
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return "", errors.New("bad key")
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}
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// step 2.
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h := []byte(v4locHeader)
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// step 3.
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n := randBytes
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if n == nil {
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n = make([]byte, v4locNonce)
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if _, err := io.ReadFull(rand.Reader, n); err != nil {
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return "", fmt.Errorf("read from crypto/rand.Reader: %w", err)
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}
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}
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// step 4.
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ek, n2, ak, err := v4locSplitKey(key, n)
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if err != nil {
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return "", fmt.Errorf("create enc and auth keys: %w", err)
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}
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// step 5.
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c := make([]byte, len(m))
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ciph, err := chacha20.NewUnauthenticatedCipher(ek, n2)
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if err != nil {
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return "", fmt.Errorf("create chacha20 cipher: %w", err)
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}
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ciph.XORKeyStream(c, m)
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// step 6.
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preAuth := pae(h, n, c, f, i)
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// step 7.
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mac, err := blake2b.New(v4locMac, ak)
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if err != nil {
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return "", fmt.Errorf("unable to in initialize MAC kdf: %w", err)
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}
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mac.Write(preAuth)
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t := mac.Sum(nil)
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// step 8.
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body := make([]byte, 0, len(n)+len(c)+len(t))
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body = append(body, n...)
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body = append(body, c...)
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body = append(body, t...)
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return buildToken(h, body, f), nil
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}
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func V4Decrypt(token string, key []byte, payload, footer any, implicit string) error {
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// step 0.
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k := key
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i := []byte(implicit)
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// step 1.
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// step 2.
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// step 3.
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if !strings.HasPrefix(token, v4locHeader) {
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return ErrIncorrectTokenFormat
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}
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h := []byte(v4locHeader)
112+
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// step 4.
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body, footerBytes, err := splitToken(token, v4locHeader)
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if err != nil {
116+
return fmt.Errorf("decode token: %w", err)
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}
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if len(body) < v4locNonce+v4locMac {
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return ErrIncorrectTokenFormat
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}
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f := footerBytes
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n := body[:v4locNonce]
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c := body[v4locNonce : len(body)-v4locMac]
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t := body[v4locNonce+len(c):]
125+
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// step 5.
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ek, n2, ak, err := v4locSplitKey(k, n)
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if err != nil {
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return fmt.Errorf("create enc and auth keys: %w", err)
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}
131+
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// step 6.
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preAuth := pae(h, n, c, f, i)
134+
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// step 7.
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hasher, err := blake2b.New(v4locMac, ak)
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if err != nil {
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return fmt.Errorf("create blake2b hash: %w", err)
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}
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hasher.Write(preAuth)
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t2 := hasher.Sum(nil)
142+
143+
// step 8.
144+
if !hmac.Equal(t, t2) {
145+
return ErrInvalidTokenAuth
146+
}
147+
148+
// step 9.
149+
ciph, err := chacha20.NewUnauthenticatedCipher(ek, n2)
150+
if err != nil {
151+
return fmt.Errorf("create chacha20 cipher: %w", err)
152+
}
153+
154+
p := make([]byte, len(c))
155+
ciph.XORKeyStream(p, c)
156+
157+
// step 10.
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if payload != nil {
159+
if err := fromBytes(p, payload); err != nil {
160+
return fmt.Errorf("decode payload: %w", err)
161+
}
162+
}
163+
164+
if footer != nil {
165+
if err := fromBytes(f, footer); err != nil {
166+
return fmt.Errorf("decode footer: %w", err)
167+
}
168+
}
169+
return nil
170+
}
171+
172+
func v4locSplitKey(key, n []byte) (ek, n2, ak []byte, err error) {
173+
encKDF, err := blake2b.New(56, key)
174+
if err != nil {
175+
return nil, nil, nil, err
176+
}
177+
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encKDF.Write([]byte("paseto-encryption-key"))
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encKDF.Write(n)
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tmp := encKDF.Sum(nil)
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ek, n2 = tmp[:v4locKDF], tmp[v4locKDF:]
182+
183+
authKDF, err := blake2b.New(32, key)
184+
if err != nil {
185+
return nil, nil, nil, err
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}
187+
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authKDF.Write([]byte("paseto-auth-key-for-aead"))
189+
authKDF.Write(n)
190+
ak = authKDF.Sum(nil)
191+
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return ek, n2, ak, nil
193+
}

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