Unify local and external keys in keybase interface (#117)

* Return errors on priv.Sign(), priv.PubKey()

* Add CreateLedger, CreateOffline

* Add switch on .Sign() for Ledger wallets

* Add offline signing switch on .Sign()

* Use MustUnmarshalBinaryBare()

* Add confirmation to delete offline/Ledger keys

* Lowercase error message

* Add human-readable .GetType() function to Info interface

* Rename CryptoAlgo => SignAlgo

* assert.Nil(t, err) => assert.NoError(t, err)

ledger_secp256k1.go

@@ -73,11 +73,7 @@ func (pk *PrivKeyLedgerSecp256k1) AssertIsPrivKeyInner() {}
 // Bytes fulfils PrivKey Interface - but it stores the cached pubkey so we can verify
 // the same key when we reconnect to a ledger
 func (pk PrivKeyLedgerSecp256k1) Bytes() []byte {
-	bin, err := cdc.MarshalBinaryBare(pk)
-	if err != nil {
-		panic(err)
-	}
-	return bin
+	return cdc.MustMarshalBinaryBare(pk)
 }
 
 // Sign calls the ledger and stores the PubKey for future use
@@ -85,39 +81,34 @@ func (pk PrivKeyLedgerSecp256k1) Bytes() []byte {
 // Communication is checked on NewPrivKeyLedger and PrivKeyFromBytes,
 // returning an error, so this should only trigger if the privkey is held
 // in memory for a while before use.
-func (pk PrivKeyLedgerSecp256k1) Sign(msg []byte) Signature {
-	// oh, I wish there was better error handling
+func (pk PrivKeyLedgerSecp256k1) Sign(msg []byte) (Signature, error) {
 	dev, err := getLedger()
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	sig, err := signLedgerSecp256k1(dev, pk.Path, msg)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	pub, err := pubkeyLedgerSecp256k1(dev, pk.Path)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	// if we have no pubkey yet, store it for future queries
 	if pk.CachedPubKey == nil {
 		pk.CachedPubKey = pub
 	} else if !pk.CachedPubKey.Equals(pub) {
-		panic("stored key does not match signing key")
+		return nil, fmt.Errorf("stored key does not match signing key")
 	}
-	return sig
+	return sig, nil
 }
 
 // PubKey returns the stored PubKey
-func (pk PrivKeyLedgerSecp256k1) PubKey() PubKey {
-	key, err := pk.getPubKey()
-	if err != nil {
-		panic(err)
-	}
-	return key
+func (pk PrivKeyLedgerSecp256k1) PubKey() (PubKey, error) {
+	return pk.getPubKey()
 }
 
 // getPubKey reads the pubkey from cache or from the ledger itself