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Merged
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Nov 6, 2025
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misc: ecdsa raw signature #1457

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1e9f2a5
add ecdsa raw signature
xinsong-cui Nov 4, 2025
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lint
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8ee1fbf
add native implementation
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pr feedback
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remove jvm test
xinsong-cui Nov 4, 2025
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cleanup
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lint
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unit test
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11 changes: 10 additions & 1 deletion runtime/runtime-core/api/runtime-core.api
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Original file line number Diff line number Diff line change
Expand Up @@ -726,7 +726,16 @@ public final class aws/smithy/kotlin/runtime/hashing/Crc32cKt {
}

public final class aws/smithy/kotlin/runtime/hashing/EcdsaJVMKt {
public static final fun ecdsaSecp256r1 ([B[B)[B
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@xinsong-cui xinsong-cui Nov 4, 2025 •
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Existing ecdsaSecp256r1(key, message) calls work unchanged, should not be a breaking change

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@ianbotsf ianbotsf Nov 4, 2025

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This is definitely a breaking change because you've altered the method signature. Older consumers of runtime-core will encounter a NoSuchMethodError exception at runtime. The only way to do this safely without breaking binary compatibility is to maintain the old method signature and add a new one.

I recommend one of the following approaches:

  • Expose a new method ecdsaSecp256r1Rs which invokes ecdsaSecp256r1Rs and extracts the r and s values. This could be implemented in common since it's just byte manipulation
  • Expose a new method asn1DerToRs which converts any ByteArray from ASN.1 DER format to r||s. Callers would then invoke ecdsaSecp256r1Rs first and then asn1DerToRs. This could also be implemented in common.

public static final fun ecdsaSecp256r1 ([B[BLaws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;)[B
public static synthetic fun ecdsaSecp256r1$default ([B[BLaws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;ILjava/lang/Object;)[B
}

public final class aws/smithy/kotlin/runtime/hashing/EcdsaSignatureType : java/lang/Enum {
public static final field ASN1_DER Laws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;
public static final field RAW_RS Laws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;
public static fun getEntries ()Lkotlin/enums/EnumEntries;
public static fun valueOf (Ljava/lang/String;)Laws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;
public static fun values ()[Laws/smithy/kotlin/runtime/hashing/EcdsaSignatureType;
}

public abstract interface class aws/smithy/kotlin/runtime/hashing/HashFunction {
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11 changes: 10 additions & 1 deletion runtime/runtime-core/common/src/aws/smithy/kotlin/runtime/hashing/Ecdsa.kt
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Expand Up @@ -4,7 +4,16 @@
*/
package aws.smithy.kotlin.runtime.hashing

public enum class EcdsaSignatureType {
ASN1_DER,
RAW_RS,
}

/**
* ECDSA on the SECP256R1 curve.
*/
public expect fun ecdsaSecp256r1(key: ByteArray, message: ByteArray): ByteArray
public expect fun ecdsaSecp256r1(
key: ByteArray,
message: ByteArray,
signatureType: EcdsaSignatureType = EcdsaSignatureType.ASN1_DER,
): ByteArray
40 changes: 38 additions & 2 deletions runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/hashing/EcdsaJVM.kt
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Expand Up @@ -12,7 +12,11 @@ import java.security.spec.*
/**
* ECDSA on the SECP256R1 curve.
*/
public actual fun ecdsaSecp256r1(key: ByteArray, message: ByteArray): ByteArray {
public actual fun ecdsaSecp256r1(
key: ByteArray,
message: ByteArray,
signatureType: EcdsaSignatureType,
): ByteArray {
// Convert private key to BigInteger
val d = BigInteger(key)

Expand All @@ -28,10 +32,42 @@ public actual fun ecdsaSecp256r1(key: ByteArray, message: ByteArray): ByteArray
val privateKey = keyFactory.generatePrivate(privateKeySpec)

// Sign the message
return Signature.getInstance("SHA256withECDSA").apply {
val derSignature = Signature.getInstance("SHA256withECDSA").apply {
initSign(privateKey)
update(message)
}.sign()

return when (signatureType) {
EcdsaSignatureType.ASN1_DER -> derSignature
EcdsaSignatureType.RAW_RS -> parseDerSignature(derSignature)
}
}

private fun BigInteger.toJvm(): java.math.BigInteger = java.math.BigInteger(1, toByteArray())

/**
* Parses an ASN.1 DER encoded ECDSA signature and converts it to raw r||s format.
*/
private fun parseDerSignature(derSignature: ByteArray): ByteArray {
var index = 2 // Skip SEQUENCE tag and length

// Read r
index++ // Skip INTEGER tag
val rLength = derSignature[index++].toInt() and 0xFF
val r = derSignature.sliceArray(index until index + rLength)
index += rLength

// Read s
index++ // Skip INTEGER tag
val sLength = derSignature[index++].toInt() and 0xFF
val s = derSignature.sliceArray(index until index + sLength)

// Remove leading zero bytes and pad to 32 bytes
val rFixed = r.dropWhile { it == 0.toByte() }.toByteArray()
val sFixed = s.dropWhile { it == 0.toByte() }.toByteArray()

val rPadded = if (rFixed.size < 32) ByteArray(32 - rFixed.size) + rFixed else rFixed
val sPadded = if (sFixed.size < 32) ByteArray(32 - sFixed.size) + sFixed else sFixed

return rPadded + sPadded
}
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@ianbotsf ianbotsf Nov 4, 2025

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Question: Where did we find this algorithm? Can we link to a reliable source?

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@xinsong-cui xinsong-cui Nov 4, 2025

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I don't really find any available algorithm, I find this is helpful: the structure of DER (which tells where is r and s located in DER)

19 changes: 19 additions & 0 deletions runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/hashing/EcdsaJVMTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
*/
package aws.smithy.kotlin.runtime.hashing

import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertFalse
import org.junit.jupiter.api.Assertions.assertTrue
import java.security.*
Expand All @@ -30,6 +31,11 @@ class EcdsaJVMTest {

assertTrue(signature.isNotEmpty())
assertTrue(signature.size >= 64) // ECDSA signatures are typically 70-72 bytes in DER format

val rawSignature = ecdsaSecp256r1(privateKey, message, EcdsaSignatureType.RAW_RS)

assertTrue(rawSignature.isNotEmpty())
assertEquals(64, rawSignature.size) // Raw signature should be exactly 64 bytes (32 bytes r + 32 bytes s)
}

@Test
Expand All @@ -44,6 +50,13 @@ class EcdsaJVMTest {
assertTrue(signature1.isNotEmpty())
assertTrue(signature2.isNotEmpty())
assertFalse(signature1.contentEquals(signature2))

val rawSignature1 = ecdsaSecp256r1(privateKey, message1, EcdsaSignatureType.RAW_RS)
val rawSignature2 = ecdsaSecp256r1(privateKey, message2, EcdsaSignatureType.RAW_RS)

assertTrue(rawSignature1.isNotEmpty())
assertTrue(rawSignature2.isNotEmpty())
assertFalse(rawSignature1.contentEquals(rawSignature2))
}

@Test
Expand All @@ -53,6 +66,9 @@ class EcdsaJVMTest {

val signature = ecdsaSecp256r1(privateKey, message)
assertTrue(signature.isNotEmpty())

val rawSignature = ecdsaSecp256r1(privateKey, message, EcdsaSignatureType.RAW_RS)
assertTrue(rawSignature.isNotEmpty())
}

@Test
Expand All @@ -62,6 +78,9 @@ class EcdsaJVMTest {

val signature = ecdsaSecp256r1(privateKey, largeMessage)
assertTrue(signature.isNotEmpty())

val rawSignature = ecdsaSecp256r1(privateKey, largeMessage, EcdsaSignatureType.RAW_RS)
assertTrue(rawSignature.isNotEmpty())
}

@Test
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