diff --git a/cryptography-providers/apple/src/commonMain/kotlin/algorithms/SecEcdsa.kt b/cryptography-providers/apple/src/commonMain/kotlin/algorithms/SecEcdsa.kt
index d1efb6b7..59f829fb 100644
--- a/cryptography-providers/apple/src/commonMain/kotlin/algorithms/SecEcdsa.kt
+++ b/cryptography-providers/apple/src/commonMain/kotlin/algorithms/SecEcdsa.kt
@@ -261,7 +261,7 @@ private class EcdsaRawSignatureGenerator(
         override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
             val signature = signToByteArray()
             checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-            signature.copyInto(destination, destinationOffset, destinationOffset)
+            signature.copyInto(destination, destinationOffset, 0, signature.size)
             return signature.size
         }
 
diff --git a/cryptography-providers/apple/src/commonMain/kotlin/internal/SecSignature.kt b/cryptography-providers/apple/src/commonMain/kotlin/internal/SecSignature.kt
index e11ab12a..1c6a32a0 100644
--- a/cryptography-providers/apple/src/commonMain/kotlin/internal/SecSignature.kt
+++ b/cryptography-providers/apple/src/commonMain/kotlin/internal/SecSignature.kt
@@ -107,7 +107,7 @@ private class SecSignFunction(
     override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
         val signature = signToByteArray()
         checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-        signature.copyInto(destination, destinationOffset, destinationOffset)
+        signature.copyInto(destination, destinationOffset, 0, signature.size)
         return signature.size
     }
 
diff --git a/cryptography-providers/jdk/src/jvmMain/kotlin/algorithms/JdkEcdsa.kt b/cryptography-providers/jdk/src/jvmMain/kotlin/algorithms/JdkEcdsa.kt
index 62fda107..133df1c4 100644
--- a/cryptography-providers/jdk/src/jvmMain/kotlin/algorithms/JdkEcdsa.kt
+++ b/cryptography-providers/jdk/src/jvmMain/kotlin/algorithms/JdkEcdsa.kt
@@ -70,7 +70,8 @@ private class EcdsaRawSignatureGenerator(
         override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
             val signature = signToByteArray()
             checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-            signature.copyInto(destination, destinationOffset, destinationOffset)
+            // Copy the whole signature into destination at the given offset
+            signature.copyInto(destination, destinationOffset, 0, signature.size)
             return signature.size
         }
 
diff --git a/cryptography-providers/jdk/src/jvmMain/kotlin/operations/JdkSignatureGenerator.kt b/cryptography-providers/jdk/src/jvmMain/kotlin/operations/JdkSignatureGenerator.kt
index a754b057..43505664 100644
--- a/cryptography-providers/jdk/src/jvmMain/kotlin/operations/JdkSignatureGenerator.kt
+++ b/cryptography-providers/jdk/src/jvmMain/kotlin/operations/JdkSignatureGenerator.kt
@@ -38,7 +38,7 @@ private class JdkSignFunction(
     override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
         val signature = signToByteArray()
         checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-        signature.copyInto(destination, destinationOffset, destinationOffset)
+        signature.copyInto(destination, destinationOffset, 0, signature.size)
         return signature.size
     }
 
diff --git a/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3AesCmac.kt b/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3AesCmac.kt
index c2896896..20656a0d 100644
--- a/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3AesCmac.kt
+++ b/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3AesCmac.kt
@@ -65,15 +65,15 @@ private class AesCmacSignature(
 
         @OptIn(UnsafeNumber::class)
         override fun update(source: ByteArray, startIndex: Int, endIndex: Int) {
-            // Implementation for updating the CMAC with the provided data
+            // Update CMAC using the requested slice [startIndex, endIndex)
             checkBounds(source.size, startIndex, endIndex)
             val context = context.access()
             source.usePinned {
                 checkError(
                     EVP_MAC_update(
                         ctx = context,
-                        data = it.safeAddressOf(0).reinterpret(),
-                        datalen = source.size.convert()
+                        data = it.safeAddressOf(startIndex).reinterpret(),
+                        datalen = (endIndex - startIndex).convert()
                     )
                 )
             }
@@ -82,7 +82,7 @@ private class AesCmacSignature(
         override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
             val signature = signToByteArray()
             checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-            signature.copyInto(destination, destinationOffset, destinationOffset)
+            signature.copyInto(destination, destinationOffset, 0, signature.size)
             return signature.size
         }
 
@@ -139,4 +139,4 @@ private class AesCmacSignature(
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3Ecdsa.kt b/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3Ecdsa.kt
index a8527387..a1de279c 100644
--- a/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3Ecdsa.kt
+++ b/cryptography-providers/openssl3/api/src/commonMain/kotlin/algorithms/Openssl3Ecdsa.kt
@@ -174,7 +174,7 @@ private class EcdsaRawSignatureGenerator(
         override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
             val signature = signToByteArray()
             checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-            signature.copyInto(destination, destinationOffset, destinationOffset)
+            signature.copyInto(destination, destinationOffset, 0, signature.size)
             return signature.size
         }
 
diff --git a/cryptography-providers/openssl3/api/src/commonMain/kotlin/operations/Openssl3DigestSignatureGenerator.kt b/cryptography-providers/openssl3/api/src/commonMain/kotlin/operations/Openssl3DigestSignatureGenerator.kt
index 13336192..07a1f6c6 100644
--- a/cryptography-providers/openssl3/api/src/commonMain/kotlin/operations/Openssl3DigestSignatureGenerator.kt
+++ b/cryptography-providers/openssl3/api/src/commonMain/kotlin/operations/Openssl3DigestSignatureGenerator.kt
@@ -46,7 +46,7 @@ internal abstract class Openssl3DigestSignatureGenerator(
         override fun signIntoByteArray(destination: ByteArray, destinationOffset: Int): Int {
             val signature = signToByteArray()
             checkBounds(destination.size, destinationOffset, destinationOffset + signature.size)
-            signature.copyInto(destination, destinationOffset, destinationOffset)
+            signature.copyInto(destination, destinationOffset, 0, signature.size)
             return signature.size
         }
 
diff --git a/cryptography-random/src/linuxAndAndroidNativeMain/kotlin/URandom.kt b/cryptography-random/src/linuxAndAndroidNativeMain/kotlin/URandom.kt
index ef2f56b2..f09bb009 100644
--- a/cryptography-random/src/linuxAndAndroidNativeMain/kotlin/URandom.kt
+++ b/cryptography-random/src/linuxAndAndroidNativeMain/kotlin/URandom.kt
@@ -51,6 +51,7 @@ private fun awaitURandomReady() {
 
 private fun open(path: String): Int {
     val fd = open(path, O_RDONLY, null)
-    if (fd <= 0) errnoCheck()
+    // According to POSIX, open returns -1 on error; 0 is a valid descriptor
+    if (fd < 0) errnoCheck()
     return fd
 }