Is it possible to derive an IPNS name from an IPFS keypair without publishing?

We would like to allow users to restore their databases from an IPNS pointer based on IPFS key names that they maintain. However, due to there being only two endpoints for IPNS name/resolve and name/publish, it doesnt appear that one can derive the IPNS name from a key without re-pointing the IPNS name. Is it possible?

I have found that the keys all exist in the keystore fodler inside of IPFS_HOME, but I'm not sure about the format of these files. The comments here suggest that they are in protobuf format, but I'm not sure how to extract the data meaningfully from there.

For example, using --decode-raw gives me this:

root@ip-172-31-11-196:~# protoc --decode_raw $IPFS_HOME/keystore/keypairfile
1: 0
2: "0\202\004\243\002\001\000\002\202\001\001\000\333\246v\\+s\350\321`8Y\224Y\353I\267h\254\257\334\356Q\276W\017ZA\357\327\331\t\304?\327Y\312tP\201\377\235^\014\376\245Q1*[n\004Lh\377\256F\350\235yr\231\233\353\237D~\321\254j\252\273I[\245rv\3046\3441WO\257\252+\273|\216\207\204z<~2K\265\362\224\016\246\334+\373JE\326\371\n\032,n\025\266\335\374\244\202\242\364>\033\275\345l\327\350\353\\\206~*h\237\223\321\337\037P\212\227\204\014W;\205\314pE\256\207\200\t\3275\256\234\'K\177E\253\355c\225\340\251\370\222\371\247\366\353\0140}\312J\254\267+\007\323\366\357\350\244>[\203\031Z\217\311\'\324_o\017\307\262\034\234F4\267\014\343\221NM\221\214\230\034D*-Pa\315%\2513\016H\311\375\004\345\243Q2\277\007\330\217\363\306\272{\357\237\252\204\332\301q\276\000\362\032\212\212\202I\031\002\003\001\000\001\002\202\001\000\002\003\247\3106\231\314\203\307\007\035C0\003\351\\&8\2270F{7l\242\366g\356d#Xd\225UK<\201\016\217\362\241%\320\246\261+jq\001\377\243Ht\032\014&\030R\001`\034\252\202a\246\206\'4\026\222T?Z\370\314p\354a\270{\377Y\372\271k\307?`+;\372\306\375=F\326wP\006F_t\203\314m\221\210\035 \232Q\264\037F/\337\356V\3028\243\226}9\037M\302\202\305Z%\355\007\010\337\316L\276\203%\233\031\216\010P\235\t\307\372\203\362\206\265\327\022W\032\327e\213k?\001\314\324k\022\303\306W\25798\350\240\357\334\311Ft\275\204\342\207^\326k-)]eD\341\007\372\377-J\261\\cJh\246\212\010\025\t\252Q\\\340\221\330\277q\t6\210${\222\225y\260\266\r\204\014P\257\262DR\307\001\216\250$\212\220\362xp\311\022\321\357*\2309\t\232\342\260\001\002\201\201\000\371p|\305\276\276*\253%\244\276\360i\203Y\002\2217$\372g\017WT!C\225\362n\377`\r\t\203(q\353\323K\202\356X\273B\341\037p\t\017\354|+_\317\313k\210\335\000Fr3pqW\001>G\243\231y\373p7\335\201K\362>\333]Od\365\255\360\373\214\245\237\267R\354GA\366\016W\371@*s05`>}\217\361\363PU2]\225\226]=\356n\005\236P\307w\353\342\001\002\201\201\000\341mfm9y\266\343\251>\314\007C\310\324\210\302\230\210\237\353\021|W\330\035w\223~\'SD9r\272\377;)\250\336)[X<XH\021a\024\3108o\261\214\007\240\301\326\222,\260e\001m\370\320\032\354\246u\231\177\337\227\371\214]\242~{o\020h@\220(-\337FF\340\221X\340\001*\t\376\350\343\345\345\224\336\261g>\276\215\252\335H\233\227\210\256\315\302\372(\376\221\265c\260\3537\031\002\201\200O9A\367\320h7\307\031\362\244NYD\305m\202O\300g\343y\304\343\314\230\331\264!:\354\367\327\020\2304\356\220\262\210\010I\230XZ\206\020\240`5]\016\255\244\242\330)\244\377\244`;$8kH\322\316\020\020\373\34475\027\036,\317\350\324\345c\005\016\336\313\016*\022\244\222\246<\2639(\374OF\263\361\207\232E)\247O[\373\235\252\343\024W\022\336\252\010\264\204\2576$3\346K\276\001\002\201\200\023\347\320\"\226\357\253y\240\351=\244\352\224bH\r>\340\331\226->\030\227\251\312tH\260zF\314\367\327\221P\r\026\257?a\244\201\367\235\255\2030\r\232\006*\334]\224\021i\274\020\234&\337 q\327\026y\215\035WG\226[\332\032M\356ZR\325\364\321\357\331\212\342\272\023\177\220\266\344\355*\315&\202\316\327\310\346#\346\".&\2716\323>\244\371\260@\316\206\266\317\326,\334z\362\351\235k\211\002\201\201\000\311\231\273\205\340\260\0360\252\236G\221\305\201!\305\013\013\\\217N\332\004\364>\314\nP\016\375-\240b\\\246=\264C\t\357\362\303xC\327P\353\034\224\023Xn\204\360\300A3\001N\262\3233r\004\346v\300v\"g\315\034\275\001L;4,\224\302\376\372\324\037Z\232\245)2\364\034\177\307\341\0045(\326\360\3311\265\002\231\265Y\014Cb%\202uB\033\313\177-kr\345\026\247\357\237\247+\310\272"

Which appears to be two binary items, but still nothing I can quite extract the IPNS name from... or is it?

Solution

Here's a working example in Go of how to read the RSA key pair and base58 encode the public key to get the IPNS peer ID:

package main

import (
    "bufio"
    "bytes"
    "encoding/pem"
    "fmt"
    "log"

    "github.com/ipfs/go-ipfs/keystore"
    b58 "github.com/mr-tron/base58/base58"
    mh "github.com/multiformats/go-multihash"
)

func main() {
    ks, err := keystore.NewFSKeystore("/Users/username/.ipfs/keystore/")
    if err != nil {
        log.Fatal(err)
    }

    priv, err := ks.Get("mykey")
    if err != nil {
        log.Fatal(err)
    }

    privBytes, err := priv.Bytes()
    if err != nil {
        log.Fatal(err)
    }

    var privPEM bytes.Buffer
    privWriter := bufio.NewWriter(&privPEM)
    pem.Encode(privWriter, &pem.Block{
        Type:  "RSA PRIVATE KEY",
        Bytes: privBytes,
    })
    privWriter.Flush()

    pub := priv.GetPublic()
    var pubPEM bytes.Buffer
    pubBytes, err := pub.Bytes()
    pubWriter := bufio.NewWriter(&pubPEM)
    pem.Encode(pubWriter, &pem.Block{
        Type:  "RSA PUBLIC KEY",
        Bytes: pubBytes,
    })
    pubWriter.Flush()

    privPEMString := string(privPEM.Bytes())
    pubPEMString := string(pubPEM.Bytes())

    var alg uint64 = mh.SHA2_256
    maxInlineKeyLength := 42
    if len(pubBytes) <= maxInlineKeyLength {
        alg = mh.ID
    }
    hash, _ := mh.Sum(pubBytes, alg, -1)
    peerID := b58.Encode(hash)

    fmt.Println(privPEMString)
    fmt.Println(pubPEMString)
    fmt.Println("IPNS:", peerID)
}

Output:

The key was generated by doing:

ipfs key gen mykey --type=rsa --size=2048

It'll be a very similar process for other languages such as Node.js