feat: add SetDERConversion to reset skipDERConversion

CHANGELOG.md

@@ -55,6 +55,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (server) [#24720](https://github.com/cosmos/cosmos-sdk/pull/24720) add `verbose_log_level` flag for configuring the log level when switching to verbose logging mode during sensitive operations (such as chain upgrades).
 * (crypto) [#24861](https://github.com/cosmos/cosmos-sdk/pull/24861) add `PubKeyFromCometTypeAndBytes` helper function to convert from `comet/v2` PubKeys to the `cryptotypes.Pubkey` interface.
 * (abci_utils) [#25008](https://github.com/cosmos/cosmos-sdk/pull/25008) add the ability to assign a custom signer extraction adapter in `DefaultProposalHandler`.
+* (crypto/ledger) [#25435](https://github.com/cosmos/cosmos-sdk/pull/25435) Add SetDERConversion to reset skipDERConversion and App name for ledger.
 
 ### Improvements
 

crypto/ledger/ledger_secp256k1.go

@@ -17,6 +17,9 @@ import (
 // options stores the Ledger Options that can be used to customize Ledger usage
 var options Options
 
+// AppName defines the Ledger app used for signing. Cosmos SDK uses the Cosmos app
+const AppName = "Cosmos"
+
 type (
 	// discoverLedgerFn defines a Ledger discovery function that returns a
 	// connected device or an error upon failure. Its allows a method to avoid CGO
@@ -66,7 +69,7 @@ func initOptionsDefault() {
 	options.createPubkey = func(key []byte) types.PubKey {
 		return &secp256k1.PubKey{Key: key}
 	}
-	options.appName = "Cosmos"
+	options.appName = AppName
 	options.skipDERConversion = false
 }
 
@@ -90,6 +93,51 @@ func SetSkipDERConversion() {
 	options.skipDERConversion = true
 }
 
+// SetDERConversion configures whether DER signature conversion should be enabled.
+// When enabled (true), signatures returned from the Ledger device are converted
+// from DER format to BER format, which is the standard behavior for Cosmos SDK chains.
+// When disabled (false), raw signatures are used without conversion, which is
+// typically required for Ethereum/EVM-compatible chains.
+//
+// Parameters:
+//   - enabled: true to enable DER conversion (Cosmos chains), false to disable (Ethereum chains)
+//
+// Example usage for different coin types in a key management CLI:
+//
+//	switch coinType {
+//	case 60:
+//	    // Ethereum/EVM chains - disable DER conversion for raw signatures
+//	    cosmosLedger.SetDiscoverLedger(func() (cosmosLedger.SECP256K1, error) {
+//	        return evmkeyring.LedgerDerivation()
+//	    })
+//	    cosmosLedger.SetCreatePubkey(func(key []byte) cryptotypes.PubKey {
+//	        return evmkeyring.CreatePubkey(key)
+//	    })
+//	    cosmosLedger.SetAppName(evmkeyring.AppName)
+//	    cosmosLedger.SetDERConversion(false) // Disable DER conversion for Ethereum
+//	case 118:
+//	    // Cosmos SDK chains - enable DER conversion for signature compatibility
+//	    cosmosLedger.SetDiscoverLedger(func() (cosmosLedger.SECP256K1, error) {
+//	        device, err := ledger.FindLedgerCosmosUserApp()
+//	        if err != nil {
+//	            return nil, err
+//	        }
+//	        return device, nil
+//	    })
+//	    cosmosLedger.SetCreatePubkey(func(key []byte) cryptotypes.PubKey {
+//	        return &secp256k1.PubKey{Key: key}
+//	    })
+//	    cosmosLedger.SetAppName(cosmosLedger.AppName)
+//	    cosmosLedger.SetDERConversion(true) // Enable DER conversion for Cosmos
+//	default:
+//	    return fmt.Errorf(
+//	        "unsupported coin type %d for Ledger. Supported coin types: 60 (Ethereum app), 118 (Cosmos app)", coinType,
+//	    )
+//	}
+func SetDERConversion(enabled bool) {
+	options.skipDERConversion = !enabled
+}
+
 // NewPrivKeySecp256k1Unsafe will generate a new key and store the public key for later use.
 //
 // This function is marked as unsafe as it will retrieve a pubkey without user verification.