Who knows what this private key is? 7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0
Half of p mod
Everyone knows
Is this the upper branch of the elliptic curve, counting from the generator point?
Yes, that's the last point
Have you considered deriving a formula such that adding the generator point to any given point results in a one‑point shift strictly towards y=0? This would allow you to determine whether the point lies on the upper or lower branch.
There is such a formula without the modulus p. However, when working with the modulus of a prime number, the presence of a square root causes complications, as it yields two roots.
kTimesG is right algebraically — (n+1)/2 is 2⁻¹ mod n and is used for halving (2R = P → R = [(n+1)/2]·P).
But after my geometric research: The points (n/2)·G and (n/2+1)·G have the exact same X coordinate (the one with leading zeros: 00000000...3b78ce563f...) — they differ only in Y parity. This is a (k, n-k) pair.
More interestingly — if you unfold the keys around n/2, you'll see perfect mirror symmetry:
n/2 - 1 ↔ n/2 + 2 (same X, flipped Y)
n/2 - 2 ↔ n/2 + 3
n/2 - 3 ↔ n/2 + 4
The point n/2 is the symmetry axis of the cyclic group — a linear walk along the curve 'turns around' right here. This is not an 'upper branch' (such a concept doesn't exist in EC), but it is the reflection point in the group structure.
So (n+1)/2 is simultaneously: the multiplicative inverse of 2 mod n (halving), and the point where the k ↔ n-k symmetry 'meets.'
[ k -15 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747153
X: 6286bb9071f8887bc4fbb3f0a9ecb19efcdd2cf15e286da71bb60c9b5ff5e644
Pub: 026286bb9071f8887bc4fbb3f0a9ecb19efcdd2cf15e286da71bb60c9b5ff5e644 -> Adr: 15fS3Hy9oSSnoDHoj9wuVBThXjH5yTyQma
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747184
Pub: 036286bb9071f8887bc4fbb3f0a9ecb19efcdd2cf15e286da71bb60c9b5ff5e644 -> Adr: 1BE8jrkpvVpm1epztSXFRSJ7eYjfMT3TkX
----------------------------------------
[ k -14 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747154
X: 3905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b
Pub: 023905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b -> Adr: 13xMdG58VuHFKESWs2wuhXbUXRP2jmGJBL
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747183
Pub: 033905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b -> Adr: 1E77TAEg7VAdUcKLGUWMnwJuY5XqDtXy9Y
----------------------------------------
[ k -13 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747155
X: 561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e
Pub: 03561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e -> Adr: 16mJRZXsiqw7TzVAZLAYeDxtHcDkAR8cbM
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747182
Pub: 02561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e -> Adr: 135yPWdDgsB7PtMUdsEAf8jxkv9wesKker
----------------------------------------
[ k -12 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747156
X: 75bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5
Pub: 0375bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5 -> Adr: 1Jh1JmV3RxMPDjgBPEHZHJRzyTQ4ynULkC
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747181
Pub: 0275bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5 -> Adr: 1LZ35k6xrj62kaUxJpG45jFhEKu9Caspw6
----------------------------------------
[ k -11 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747157
X: e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3
Pub: 02e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3 -> Adr: 1FewTQmntAiBarXqNCeC7YQfDd26kbsxRN
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747180
Pub: 03e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3 -> Adr: 17HemTH2qLRSdTPWw8B1fseBjoZWHGuuNE
----------------------------------------
[ k -10 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747158
X: 1fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e
Pub: 021fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e -> Adr: 131BCaYih8kkF8Er5nzdWkuYSW3Ngmhyqe
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747179
Pub: 031fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e -> Adr: 1BmdayqdTekMjor84epMyG9qjkhNnBMpTr
----------------------------------------
[ k -9 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747159
X: 1c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c
Pub: 031c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c -> Adr: 17jrgGw1wCK5eexxXVitD2TKsxfCxC8fq7
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747178
Pub: 021c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c -> Adr: 19KKCz4AcXTnqqs1i2DfSzBdbCeKaJNZ8q
----------------------------------------
[ k -8 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747160
X: 41f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8
Pub: 0241f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8 -> Adr: 16vVZ7R2q3DLLHX5PW1xA8uYLKV5Vp8zWc
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747177
Pub: 0341f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8 -> Adr: 1Krnz5cgFehW3jVMaFUVZgY85KvAS6FrNy
----------------------------------------
[ k -7 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747161
X: e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60
Pub: 02e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60 -> Adr: 14owJG3qQCU4nXz8esjFiL85dEezjj5kxa
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747176
Pub: 03e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60 -> Adr: 1BF2E5wfufEGgiroV1YjtGttRuWYgJ36hR
----------------------------------------
[ k -6 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747162
X: eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae
Pub: 02eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae -> Adr: 17FNBNmR1FvJvc1jZ88uGsVeWnY8uiscV3
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747175
Pub: 03eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae -> Adr: 19FqQtumUjgtwQK5wJvSRvjFvksNuHUE94
----------------------------------------
[ k -5 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747163
X: 5702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef
Pub: 035702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef -> Adr: 1JCHSxKTt6orSkg9QHhennEZdybz2zSEbD
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747174
Pub: 025702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef -> Adr: 1AXP4CRCPVA2KmfCJwCX2Taw6kmtZZbdkM
----------------------------------------
[ k -4 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747164
X: 66954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859
Pub: 0266954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859 -> Adr: 1Eepuc2uUoPfSRCUFHiuX5wtPt1hU8xdEd
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747173
Pub: 0366954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859 -> Adr: 18nHHZTwsNQwRFozvMjkUV7d8BwEPBpDft
----------------------------------------
[ k -3 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747165
X: 592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031
Pub: 02592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031 -> Adr: 1MiZBmHMMCmRSqmD5K1MwNgs2EEnm3Am1H
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747172
Pub: 03592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031 -> Adr: 18kSSgqXCr43XgesM2aFnDdebevBu4hXYn
----------------------------------------
[ k -2 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747166
X: 5699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5
Pub: 025699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5 -> Adr: 12NqA1nEZw2w2o2BrkmymQHDTMgcxBSH6w
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747171
Pub: 035699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5 -> Adr: 1LtmtRzYDJLEw6cjoD8AxqzAsL4NEBvRab
----------------------------------------
[ k -1 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747167
X: c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413
Pub: 03c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413 -> Adr: 1AsPTrDFPaz6uYyuNgnmnrt8mEkfjYFmYq
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747170
Pub: 02c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413 -> Adr: 134yamsYAgAyWVr7z4KjH6h52UigkEnrL5
----------------------------------------
[ k +0 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747168
X: 00000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63
Pub: 0300000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63 -> Adr: 1LVAsnUyEtJgZ9HzLfbtiJZuZMzHLX1n6k
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747169
Pub: 0200000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63 -> Adr: 13see6qjfupx1YWgRefwEkccZeM8QGTAiJ
----------------------------------------
[ k +1 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747169
X: 00000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63
Pub: 0200000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63 -> Adr: 13see6qjfupx1YWgRefwEkccZeM8QGTAiJ
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747168
Pub: 0300000000000000000000003b78ce563f89a0ed9414f5aa28ad0d96d6795f9c63 -> Adr: 1LVAsnUyEtJgZ9HzLfbtiJZuZMzHLX1n6k
----------------------------------------
[ k +2 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747170
X: c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413
Pub: 02c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413 -> Adr: 134yamsYAgAyWVr7z4KjH6h52UigkEnrL5
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747167
Pub: 03c62c910e502cb615a27c58512b6cc2c94f5742f76cb3d12ec993400a3695d413 -> Adr: 1AsPTrDFPaz6uYyuNgnmnrt8mEkfjYFmYq
----------------------------------------
[ k +3 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747171
X: 5699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5
Pub: 035699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5 -> Adr: 1LtmtRzYDJLEw6cjoD8AxqzAsL4NEBvRab
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747166
Pub: 025699b93fc6e1bd29e09a328d657a607b4155b61a6b5fcbedd7c12df7c67df8f5 -> Adr: 12NqA1nEZw2w2o2BrkmymQHDTMgcxBSH6w
----------------------------------------
[ k +4 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747172
X: 592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031
Pub: 03592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031 -> Adr: 18kSSgqXCr43XgesM2aFnDdebevBu4hXYn
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747165
Pub: 02592152c398d6c719636a03a6dad64246a5a6814aa62c156b0ce5332f6759b031 -> Adr: 1MiZBmHMMCmRSqmD5K1MwNgs2EEnm3Am1H
----------------------------------------
[ k +5 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747173
X: 66954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859
Pub: 0366954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859 -> Adr: 18nHHZTwsNQwRFozvMjkUV7d8BwEPBpDft
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747164
Pub: 0266954eca0543426304036fc70fc0fe3381f5195e88433bc32c5a8a60341e2859 -> Adr: 1Eepuc2uUoPfSRCUFHiuX5wtPt1hU8xdEd
----------------------------------------
[ k +6 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747174
X: 5702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef
Pub: 025702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef -> Adr: 1AXP4CRCPVA2KmfCJwCX2Taw6kmtZZbdkM
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747163
Pub: 035702fb8a2602f41f52699f688d4b005a128762e11dfd13fd22ea751ccbedb2ef -> Adr: 1JCHSxKTt6orSkg9QHhennEZdybz2zSEbD
----------------------------------------
[ k +7 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747175
X: eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae
Pub: 03eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae -> Adr: 19FqQtumUjgtwQK5wJvSRvjFvksNuHUE94
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747162
Pub: 02eb3bc68c623b1f46ab905412c7f2d588fa25abb77a7bd782ba9bb3aac05a70ae -> Adr: 17FNBNmR1FvJvc1jZ88uGsVeWnY8uiscV3
----------------------------------------
[ k +8 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747176
X: e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60
Pub: 03e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60 -> Adr: 1BF2E5wfufEGgiroV1YjtGttRuWYgJ36hR
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747161
Pub: 02e5cbd62789c6a84325a2440789b88dbb1dc55afb9e8296e6bb8af7de57a50e60 -> Adr: 14owJG3qQCU4nXz8esjFiL85dEezjj5kxa
----------------------------------------
[ k +9 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747177
X: 41f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8
Pub: 0341f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8 -> Adr: 1Krnz5cgFehW3jVMaFUVZgY85KvAS6FrNy
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747160
Pub: 0241f7fa0a9a59513ae221e3b84b91995fc9d40eb5d120a6d8e663452ad92099c8 -> Adr: 16vVZ7R2q3DLLHX5PW1xA8uYLKV5Vp8zWc
----------------------------------------
[ k +10 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747178
X: 1c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c
Pub: 021c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c -> Adr: 19KKCz4AcXTnqqs1i2DfSzBdbCeKaJNZ8q
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747159
Pub: 031c2bd878b94169da722a9de0c4e317cea8802aa96045830111a89d1d9de4270c -> Adr: 17jrgGw1wCK5eexxXVitD2TKsxfCxC8fq7
----------------------------------------
[ k +11 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747179
X: 1fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e
Pub: 031fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e -> Adr: 1BmdayqdTekMjor84epMyG9qjkhNnBMpTr
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747158
Pub: 021fb527e94e9c70e8657de7458b81ef9ee3c2b4e0128a675bf7e28980e18b201e -> Adr: 131BCaYih8kkF8Er5nzdWkuYSW3Ngmhyqe
----------------------------------------
[ k +12 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747180
X: e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3
Pub: 03e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3 -> Adr: 17HemTH2qLRSdTPWw8B1fseBjoZWHGuuNE
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747157
Pub: 02e881a840847aa2e22417cd3d3e798c561e6302905dff6bf7754d941998d401e3 -> Adr: 1FewTQmntAiBarXqNCeC7YQfDd26kbsxRN
----------------------------------------
[ k +13 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747181
X: 75bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5
Pub: 0275bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5 -> Adr: 1LZ35k6xrj62kaUxJpG45jFhEKu9Caspw6
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747156
Pub: 0375bdfa066a1a42a750f283e83ec91cc0a5b688296e6aa24a28a61e3365f378e5 -> Adr: 1Jh1JmV3RxMPDjgBPEHZHJRzyTQ4ynULkC
----------------------------------------
[ k +14 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747182
X: 561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e
Pub: 02561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e -> Adr: 135yPWdDgsB7PtMUdsEAf8jxkv9wesKker
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747155
Pub: 03561a2ccdca12b67fdad28ee2c3cee78acf8117669e4a2543c81b1ca6eb4bd16e -> Adr: 16mJRZXsiqw7TzVAZLAYeDxtHcDkAR8cbM
----------------------------------------
[ k +15 ]
k: 57896044618658097711785492504343953926418782139537452191302581570759080747183
X: 3905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b
Pub: 033905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b -> Adr: 1E77TAEg7VAdUcKLGUWMnwJuY5XqDtXy9Y
n-k: 57896044618658097711785492504343953926418782139537452191302581570759080747154
Pub: 023905682b72282a782b8d8dba72cf147ade0025dca21521e1ea989040c248852b -> Adr: 13xMdG58VuHFKESWs2wuhXbUXRP2jmGJBL
----------------------------------------