Nokia C1 Plus

Nokia C3 is an entry-level device released in December 2020.

vbmeta signature parsing
Following content is parsed from HMDSW_YDU-1020-0-00WW-B01_600WW_10_20201005_sprocomm_E5531N.[SHA256SUM].7z firmware. Hope it can be helpful for bootloader unlock key calculation. Apparently it has totally different public key to Nokia C3. Minimum libavb version:  1.0 Header Block:            256 bytes Authentication Block:    576 bytes Auxiliary Block:         14720 bytes Algorithm:               SHA256_RSA4096 Rollback Index:          1 Flags:                   0 Release String:          'avbtool 1.1.0' Descriptors: Chain Partition descriptor: Partition Name:         boot Rollback Index Location: 1 Public key (sha1):      699bbdf072c365d4fae05b79e9d7910584b10029 Chain Partition descriptor: Partition Name:         dtbo Rollback Index Location: 9 Public key (sha1):      699bbdf072c365d4fae05b79e9d7910584b10029 Chain Partition descriptor: Partition Name:         recovery Rollback Index Location: 2 Public key (sha1):      6129462d828b8223f699478d0b7f2a29e537a019 Chain Partition descriptor: Partition Name:         socko Rollback Index Location: 10 Public key (sha1):      1c3918395babc94eb9b404de5aa0e15ca9c432a9 Chain Partition descriptor: Partition Name:         odmko Rollback Index Location: 11 Public key (sha1):      192c0f072043eb8231391f70d5539274084220fd Chain Partition descriptor: Partition Name:         vbmeta_system Rollback Index Location: 3 Public key (sha1):      7b160e8ec2378ced03dd448fa496ceafc3347f25 Chain Partition descriptor: Partition Name:         vbmeta_vendor Rollback Index Location: 4 Public key (sha1):      05740a1b2bf486bde0024976a8793ba7296302cd Chain Partition descriptor: Partition Name:         vbmeta_custom1 Rollback Index Location: 12 Public key (sha1):      df1a5d353a5741f2b68d9902d03b19d45770ff13 Chain Partition descriptor: Partition Name:         l_modem Rollback Index Location: 5 Public key (sha1):      f08959e3eca7feca8d8070552419601b61bbfe59 Chain Partition descriptor: Partition Name:         l_ldsp Rollback Index Location: 6 Public key (sha1):      f08959e3eca7feca8d8070552419601b61bbfe59 Chain Partition descriptor: Partition Name:         l_gdsp Rollback Index Location: 7 Public key (sha1):      f08959e3eca7feca8d8070552419601b61bbfe59 Chain Partition descriptor: Partition Name:         pm_sys Rollback Index Location: 8 Public key (sha1):      f08959e3eca7feca8d8070552419601b61bbfe59

Bootloader Unlock Theory
You may use the special fastboot binary compiled by Unisoc, which contains this command: fastboot flashing unlock_bootloader /path/to/unlock/key/file

Unisoc has a Linux binary available, in fact fastboot-android.exe contained in OST LA also has this command available.