Unify checksum helper methods

src/BizHawk.BizInvoke/WaterboxUtils.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Security.Cryptography;
 
 namespace BizHawk.BizInvoke
 {
@@ -22,18 +21,6 @@ namespace BizHawk.BizInvoke
 			}
 		}
 
-		public static byte[] Hash(byte[] data)
-		{
-			using var h = SHA1.Create();
-			return h.ComputeHash(data);
-		}
-
-		public static byte[] Hash(Stream s)
-		{
-			using var h = SHA1.Create();
-			return h.ComputeHash(s);
-		}
-
 		public static unsafe void ZeroMemory(IntPtr mem, long length)
 		{
 			byte* p = (byte*)mem;

src/BizHawk.Client.Common/Api/Classes/MemoryApi.cs

@@ -1,10 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Security.Cryptography;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.Common
@@ -235,8 +233,7 @@ namespace BizHawk.Client.Common
 			}
 			var data = new byte[count];
 			for (var i = 0; i < count; i++) data[i] = d.PeekByte(addr + i);
-			using var hasher = SHA256.Create();
+			return SHA256Checksum.ComputeDigestHex(data);
-			return hasher.ComputeHash(data).BytesToHexString();
 		}
 
 		public uint ReadByte(long addr, string domain = null) => ReadUnsigned(addr, 1, domain);

src/BizHawk.Client.Common/RomLoader.cs

@@ -233,7 +233,7 @@ namespace BizHawk.Client.Common
 			var discType = new DiscIdentifier(disc).DetectDiscType();
 			var discHasher = new DiscHasher(disc);
 			var discHash = discType == DiscType.SonyPSX
-				? discHasher.Calculate_PSX_BizIDHash().ToString("X8")
+				? discHasher.Calculate_PSX_BizIDHash()
 				: discHasher.OldHash();
 
 			var game = Database.CheckDatabase(discHash);

src/BizHawk.Client.Common/XmlGame.cs

@@ -5,7 +5,6 @@ using System.Linq;
 using System.Xml;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Common.IOExtensions;
 using BizHawk.Emulation.Common;
 
@@ -99,12 +98,11 @@ namespace BizHawk.Client.Common
 
 						ret.Assets.Add(new KeyValuePair<string, byte[]>(filename, data));
 						ret.AssetFullPaths.Add(fullPath);
-						using var sha1 = System.Security.Cryptography.SHA1.Create();
+						var sha1 = SHA1Checksum.Compute(data);
-						sha1.TransformFinalBlock(data, 0, data.Length);
+						hashStream.Write(sha1, 0, sha1.Length);
-						hashStream.Write(sha1.Hash, 0, sha1.Hash.Length);
 					}
 
-					ret.GI.Hash = hashStream.GetBuffer().HashSHA1(0, (int)hashStream.Length);
+					ret.GI.Hash = SHA1Checksum.ComputeDigestHex(hashStream.GetBufferAsSpan());
 					hashStream.Close();
 					if (originalIndex != null)
 					{

src/BizHawk.Client.Common/fwmanager/FirmwareManager.cs

@@ -1,14 +1,13 @@
 #nullable enable
 
-using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Security.Cryptography;
 using System.IO;
 using System.Linq;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Common.CollectionExtensions;
+using BizHawk.Common.IOExtensions;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.Common
@@ -20,9 +19,7 @@ namespace BizHawk.Client.Common
 		public static (byte[] Patched, string ActualHash) PerformPatchInMemory(byte[] @base, in FirmwarePatchOption patchOption)
 		{
 			var patched = patchOption.Patches.Aggregate(seed: @base, (a, fpd) => fpd.ApplyToMutating(a));
-			using var sha1 = SHA1.Create();
+			return (patched, SHA1Checksum.ComputeDigestHex(patched));
-			sha1.ComputeHash(patched);
-			return (patched, sha1.Hash.BytesToHexString());
 		}
 
 		public static (string FilePath, int FileSize, FirmwareFile FF) PerformPatchOnDisk(string baseFilename, in FirmwarePatchOption patchOption, PathEntryCollection pathEntries)
@@ -95,26 +92,16 @@ namespace BizHawk.Client.Common
 			return resolved.FilePath;
 		}
 
-		private sealed class RealFirmwareReader : IDisposable
+		private sealed class RealFirmwareReader
 		{
 			private readonly Dictionary<string, RealFirmwareFile> _dict = new();
 
-			private SHA1? _sha1 = SHA1.Create();
-
 			public IReadOnlyDictionary<string, RealFirmwareFile> Dict => _dict;
 
-			public void Dispose()
-			{
-				_sha1?.Dispose();
-				_sha1 = null;
-			}
-
 			public RealFirmwareFile Read(FileInfo fi)
 			{
-				if (_sha1 == null) throw new ObjectDisposedException(nameof(RealFirmwareReader));
 				using var fs = fi.OpenRead();
-				_sha1!.ComputeHash(fs);
+				var hash = SHA1Checksum.ComputeDigestHex(fs.ReadAllBytes());
-				var hash = _sha1.Hash.BytesToHexString();
 				return _dict![hash] = new RealFirmwareFile(fi, hash);
 			}
 		}
@@ -133,7 +120,7 @@ namespace BizHawk.Client.Common
 				if (!_firmwareSizes.Contains(fi.Length)) return false;
 
 				// check the hash
-				using var reader = new RealFirmwareReader();
+				var reader = new RealFirmwareReader();
 				reader.Read(fi);
 				var hash = reader.Dict.Values.First().Hash;
 				return FirmwareDatabase.FirmwareFiles.Any(a => a.Hash == hash);
@@ -146,7 +133,7 @@ namespace BizHawk.Client.Common
 
 		public void DoScanAndResolve(PathEntryCollection pathEntries, IDictionary<string, string> userSpecifications)
 		{
-			using var reader = new RealFirmwareReader();
+			var reader = new RealFirmwareReader();
 
 			// build a list of files under the global firmwares path, and build a hash for each of them (as ResolutionInfo) while we're at it
 			var todo = new Queue<DirectoryInfo>(new[] { new DirectoryInfo(pathEntries.AbsolutePathFor(pathEntries.FirmwaresPathFragment, null)) });

src/BizHawk.Client.EmuHawk/MainForm.Debug.cs

@@ -5,12 +5,11 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Security.Cryptography;
 using System.Windows.Forms;
 
 using BizHawk.Client.Common;
 using BizHawk.Client.EmuHawk.Properties;
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores;
 using BizHawk.Emulation.Cores.Nintendo.GBA;
@@ -88,9 +87,7 @@ namespace BizHawk.Client.EmuHawk
 							return;
 						}
 						// else something happened, figure out what it was
-						using var sha1 = SHA1.Create();
+						var baseHash = SHA1Checksum.ComputeDigestHex(@base);
-						sha1.ComputeHash(@base);
-						var baseHash = sha1.Hash.BytesToHexString();
 						this.ModalMessageBox(baseHash == fpo.BaseHash
 							? $"patchset declared with target\nSHA1:{fpo.TargetHash}\nbut produced\nSHA1:{actualHash}\n(is the patch wrong, or the hash?)"
 							: $"patchset declared for base\nSHA1:{fpo.BaseHash}\nbut\nSHA1:{baseHash}\nwas provided");

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -3822,8 +3822,9 @@ namespace BizHawk.Client.EmuHawk
 							else
 							{
 								xSw.WriteLine(xmlGame.Assets[xg].Key);
-								xSw.WriteLine($"SHA1:{xmlGame.Assets[xg].Value.HashSHA1()}");
+								var data = xmlGame.Assets[xg].Value;
-								xSw.WriteLine($"MD5:{xmlGame.Assets[xg].Value.HashMD5()}");
+								xSw.WriteLine(SHA1Checksum.ComputePrefixedHex(data));
+								xSw.WriteLine(MD5Checksum.ComputePrefixedHex(data));
 								xSw.WriteLine();
 							}
 						}
@@ -3857,7 +3858,7 @@ namespace BizHawk.Client.EmuHawk
 					var romDetails = Emulator.RomDetails();
 					if (string.IsNullOrWhiteSpace(romDetails) && loader.Rom != null)
 					{
-						_defaultRomDetails = $"{loader.Game.Name}\r\nSHA1:{loader.Rom.RomData.HashSHA1()}\r\nMD5:{loader.Rom.RomData.HashMD5()}\r\n";
+						_defaultRomDetails = $"{loader.Game.Name}\r\n{SHA1Checksum.ComputePrefixedHex(loader.Rom.RomData)}\r\n{MD5Checksum.ComputePrefixedHex(loader.Rom.RomData)}\r\n";
 					}
 					else if (string.IsNullOrWhiteSpace(romDetails) && loader.Rom == null)
 					{

src/BizHawk.Client.EmuHawk/tools/PCE/PCESoundDebugger.cs

@@ -5,7 +5,7 @@ using System.Collections.Generic;
 using System.Windows.Forms;
 
 using BizHawk.Client.Common;
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Cores.PCEngine;
 using BizHawk.Emulation.Common;
 
@@ -103,7 +103,7 @@ namespace BizHawk.Client.EmuHawk
 				}
 
 				bw.Flush();
-				string md5 = _waveformTemp.HashMD5();
+				var md5 = MD5Checksum.ComputeDigestHex(_waveformTemp);
 
 				if (!_psgEntryTable.TryGetValue(md5, out var entry))
 				{

src/BizHawk.Common/Extensions/BufferExtensions.cs

@@ -1,7 +1,6 @@
 using System;
 using System.IO;
 using System.Text;
-using System.Security.Cryptography;
 
 namespace BizHawk.Common.BufferExtensions
 {
@@ -77,30 +76,6 @@ namespace BizHawk.Common.BufferExtensions
 			return result >= pattern.Length - 1;
 		}
 
-		public static string HashMD5(this byte[] data, int offset, int len)
-		{
-			using var md5 = MD5.Create();
-			md5.ComputeHash(data, offset, len);
-			return md5.Hash.BytesToHexString();
-		}
-
-		public static string HashMD5(this byte[] data)
-		{
-			return HashMD5(data, 0, data.Length);
-		}
-
-		public static string HashSHA1(this byte[] data, int offset, int len)
-		{
-			using var sha1 = SHA1.Create();
-			sha1.ComputeHash(data, offset, len);
-			return sha1.Hash.BytesToHexString();
-		}
-
-		public static string HashSHA1(this byte[] data)
-		{
-			return HashSHA1(data, 0, data.Length);
-		}
-
 		private static int Hex2Int(char c)
 		{
 			if (c <= '9')

src/BizHawk.Common/Extensions/IOExtensions.cs

@@ -1,10 +1,14 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Text;
 
 namespace BizHawk.Common.IOExtensions
 {
 	public static class IOExtensions
 	{
+		public static Span<byte> GetBufferAsSpan(this MemoryStream ms)
+			=> ms.GetBuffer().AsSpan().Slice(start: 0, length: (int) ms.Length);
+
 		public static byte[] ReadAllBytes(this Stream stream)
 		{
 			const int BUFF_SIZE = 4096;

src/BizHawk.Common/checksums/CRC32Checksum.cs

@@ -0,0 +1,30 @@
+using System;
+
+using BizHawk.Common.BufferExtensions;
+
+namespace BizHawk.Common
+{
+	/// <summary>uses <see cref="CRC32">custom implementation</see> of CRC-32 (i.e. POSIX cksum)</summary>
+	/// <seealso cref="MD5Checksum"/>
+	/// <seealso cref="SHA1Checksum"/>
+	/// <seealso cref="SHA256Checksum"/>
+	public static class CRC32Checksum
+	{
+		/// <remarks>in bits</remarks>
+		internal const int EXPECTED_LENGTH = 32;
+
+		internal const string PREFIX = "CRC32";
+
+		public static byte[] BytesAsDigest(uint digest)
+			=> BitConverter.GetBytes(digest);
+
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> BytesAsDigest(CRC32.Calculate(data));
+
+		public static string ComputeDigestHex(ReadOnlySpan<byte> data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(ReadOnlySpan<byte> data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+	}
+}

src/BizHawk.Common/checksums/MD5Checksum.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Diagnostics;
+using System.Security.Cryptography;
+
+using BizHawk.Common.BufferExtensions;
+
+namespace BizHawk.Common
+{
+	/// <summary>uses <see cref="MD5"/> implementation from BCL</summary>
+	/// <seealso cref="CRC32Checksum"/>
+	/// <seealso cref="SHA1Checksum"/>
+	/// <seealso cref="SHA256Checksum"/>
+	public static class MD5Checksum
+	{
+		/// <remarks>in bits</remarks>
+		internal const int EXPECTED_LENGTH = 128;
+
+		internal const string PREFIX = "MD5";
+
+#if NET5_0
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> MD5.HashData(data);
+#else
+		private static MD5? _md5Impl;
+
+		private static MD5 MD5Impl
+		{
+			get
+			{
+				if (_md5Impl == null)
+				{
+					_md5Impl = MD5.Create();
+					Debug.Assert(_md5Impl.CanReuseTransform && _md5Impl.HashSize is EXPECTED_LENGTH);
+				}
+				return _md5Impl;
+			}
+		}
+
+		public static byte[] Compute(byte[] data)
+			=> MD5Impl.ComputeHash(data);
+
+		public static string ComputeDigestHex(byte[] data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(byte[] data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> Compute(data.ToArray());
+#endif
+
+		public static string ComputeDigestHex(ReadOnlySpan<byte> data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(ReadOnlySpan<byte> data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+	}
+}

src/BizHawk.Common/checksums/SHA1Checksum.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Diagnostics;
+using System.Security.Cryptography;
+
+using BizHawk.Common.BufferExtensions;
+
+namespace BizHawk.Common
+{
+	/// <summary>uses <see cref="SHA1"/> implementation from BCL</summary>
+	/// <seealso cref="CRC32Checksum"/>
+	/// <seealso cref="MD5Checksum"/>
+	/// <seealso cref="SHA256Checksum"/>
+	public static class SHA1Checksum
+	{
+		/// <remarks>in bits</remarks>
+		internal const int EXPECTED_LENGTH = 160;
+
+		internal const string PREFIX = "SHA1";
+
+#if NET5_0
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> SHA1.HashData(data);
+
+		public static byte[] ComputeConcat(ReadOnlySpan<byte> dataA, ReadOnlySpan<byte> dataB)
+		{
+			using var impl = IncrementalHash.CreateHash(HashAlgorithmName.SHA1);
+			impl.AppendData(dataA);
+			impl.AppendData(dataB);
+			return impl.GetHashAndReset();
+		}
+#else
+		private static SHA1? _sha1Impl;
+
+		private static SHA1 SHA1Impl
+		{
+			get
+			{
+				if (_sha1Impl == null)
+				{
+					_sha1Impl = SHA1.Create();
+					Debug.Assert(_sha1Impl.CanReuseTransform && _sha1Impl.HashSize is EXPECTED_LENGTH);
+				}
+				return _sha1Impl;
+			}
+		}
+
+		public static byte[] Compute(byte[] data)
+			=> SHA1Impl.ComputeHash(data);
+
+		public static byte[] ComputeConcat(byte[] dataA, byte[] dataB)
+		{
+			using var impl = IncrementalHash.CreateHash(HashAlgorithmName.SHA1);
+			impl.AppendData(dataA);
+			impl.AppendData(dataB);
+			return impl.GetHashAndReset();
+		}
+
+		public static string ComputeDigestHex(byte[] data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(byte[] data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> Compute(data.ToArray());
+
+		public static byte[] ComputeConcat(ReadOnlySpan<byte> dataA, ReadOnlySpan<byte> dataB)
+			=> ComputeConcat(dataA.ToArray(), dataB.ToArray());
+#endif
+
+		public static string ComputeDigestHex(ReadOnlySpan<byte> data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(ReadOnlySpan<byte> data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+	}
+}

src/BizHawk.Common/checksums/SHA256Checksum.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Diagnostics;
+using System.Security.Cryptography;
+
+using BizHawk.Common.BufferExtensions;
+
+namespace BizHawk.Common
+{
+	/// <summary>uses <see cref="SHA256"/> implementation from BCL</summary>
+	/// <seealso cref="CRC32Checksum"/>
+	/// <seealso cref="MD5Checksum"/>
+	/// <seealso cref="SHA1Checksum"/>
+	public static class SHA256Checksum
+	{
+		/// <remarks>in bits</remarks>
+		internal const int EXPECTED_LENGTH = 256;
+
+		internal const string PREFIX = "SHA256";
+
+#if NET5_0
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> SHA256.HashData(data);
+#else
+		private static SHA256? _sha256Impl;
+
+		private static SHA256 SHA256Impl
+		{
+			get
+			{
+				if (_sha256Impl == null)
+				{
+					_sha256Impl = SHA256.Create();
+					Debug.Assert(_sha256Impl.CanReuseTransform && _sha256Impl.HashSize is EXPECTED_LENGTH);
+				}
+				return _sha256Impl;
+			}
+		}
+
+		public static byte[] Compute(byte[] data)
+			=> SHA256Impl.ComputeHash(data);
+
+		public static string ComputeDigestHex(byte[] data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(byte[] data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> Compute(data.ToArray());
+#endif
+
+		public static string ComputeDigestHex(ReadOnlySpan<byte> data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(ReadOnlySpan<byte> data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+	}
+}

src/BizHawk.Emulation.Common/Database/Database.cs

@@ -9,7 +9,6 @@ using System.Text;
 using System.Threading;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 
 namespace BizHawk.Emulation.Common
 {
@@ -191,19 +190,19 @@ namespace BizHawk.Emulation.Common
 		{
 			acquire.WaitOne();
 
-			var hashCRC32 = $"{CRC32.Calculate(romData):X8}";
+			var hashCRC32 = CRC32Checksum.ComputeDigestHex(romData);
 			if (DB.TryGetValue(hashCRC32, out var cgi))
 			{
 				return new GameInfo(cgi);
 			}
 
-			var hashMD5 = romData.HashMD5();
+			var hashMD5 = MD5Checksum.ComputeDigestHex(romData);
 			if (DB.TryGetValue(hashMD5, out cgi))
 			{
 				return new GameInfo(cgi);
 			}
 
-			var hashSHA1 = romData.HashSHA1();
+			var hashSHA1 = SHA1Checksum.ComputeDigestHex(romData);
 			if (DB.TryGetValue(hashSHA1, out cgi))
 			{
 				return new GameInfo(cgi);

src/BizHawk.Emulation.Cores/Computers/Commodore64/C64.cs

@@ -2,7 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge;
 using BizHawk.Emulation.Cores.Computers.Commodore64.Media;
@@ -60,8 +60,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 
 			if (_board.CartPort.IsConnected)
 			{
-				// There are no multi-cart cart games, so just hardcode .First()
+				var first = _roms[0]; // There are no multi-cart cart games, so just hardcode first
-				RomDetails = $"{lp.Game.Name}\r\nSHA1:{_roms.First().HashSHA1()}\r\nMD5:{_roms.First().HashMD5()}\r\nMapper Impl \"{_board.CartPort.CartridgeType}\"";
+				RomDetails = $"{lp.Game.Name}\r\n{SHA1Checksum.ComputePrefixedHex(first)}\r\n{MD5Checksum.ComputePrefixedHex(first)}\r\nMapper Impl \"{_board.CartPort.CartridgeType}\"";
 			}
 
 			SetupMemoryDomains();

src/BizHawk.Emulation.Cores/Consoles/Atari/2600/Atari2600.Core.cs

@@ -1,7 +1,7 @@
 using System;
 
+using BizHawk.Common;
 using BizHawk.Common.NumberExtensions;
-using BizHawk.Common.BufferExtensions;
 
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.M6502;
@@ -220,7 +220,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 			HardReset();
 
-			RomDetails = $"{_game.Name}\r\nSHA1:{Rom.HashSHA1()}\r\nMD5:{Rom.HashMD5()}\r\nMapper Impl \"{_mapper.GetType()}\"";
+			RomDetails = $"{_game.Name}\r\n{SHA1Checksum.ComputePrefixedHex(Rom)}\r\n{MD5Checksum.ComputePrefixedHex(Rom)}\r\nMapper Impl \"{_mapper.GetType()}\"";
 
 			// Some games (ex. 3D tic tac toe), turn off the screen for extended periods, so we need to allow for this here.
 			if (_game.GetOptions().TryGetValue("SP_FRAME", out var spFrameStr) && spFrameStr == "true")

src/BizHawk.Emulation.Cores/Consoles/Atari/2600/Atari2600.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Linq;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Emulation.Cores.Atari.Atari2600
@@ -13,11 +13,11 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 	{
 		internal static class RomChecksums
 		{
-			public const string CongoBongo = /*sha1:*/"3A77DB43B6583E8689435F0F14AA04B9E57BDDED";
+			public const string CongoBongo = "SHA1:3A77DB43B6583E8689435F0F14AA04B9E57BDDED";
 
-			public const string KangarooNotInGameDB = /*sha1:*/"982B8016B393A9AA7DD110295A53C4612ECF2141";
+			public const string KangarooNotInGameDB = "SHA1:982B8016B393A9AA7DD110295A53C4612ECF2141";
 
-			public const string Tapper = /*sha1:*/"E986E1818E747BEB9B33CE4DFF1CDC6B55BDB620";
+			public const string Tapper = "SHA1:E986E1818E747BEB9B33CE4DFF1CDC6B55BDB620";
 		}
 
 		[CoreConstructor(VSystemID.Raw.A26)]
@@ -43,7 +43,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				game.AddOption("m", DetectMapper(rom));
 			}
 
-			var romHashSHA1 = Rom.HashSHA1();
+			var romHashSHA1 = SHA1Checksum.ComputePrefixedHex(Rom);
 			if (romHashSHA1 is RomChecksums.CongoBongo or RomChecksums.Tapper or RomChecksums.KangarooNotInGameDB)
 			{
 				game.RemoveOption("m");
@@ -82,7 +82,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				Name = _game.Name,
 				System = VSystemID.Raw.A26,
 				MetaData = "m=" + _mapper.GetType().ToString().Split('.').Last(),
-				Hash = Rom.HashSHA1(),
+				Hash = SHA1Checksum.ComputeDigestHex(Rom),
 				Region = _game.Region,
 				Status = RomStatus.Unknown
 			};

src/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/A7800Hawk.cs

@@ -1,6 +1,6 @@
 using System;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.M6502;
 using BizHawk.Common.NumberExtensions;
@@ -14,9 +14,9 @@ namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
 	{
 		internal static class RomChecksums
 		{
-			public const string KaratekaPAL = "md5:5E0A1E832BBCEA6FACB832FDE23A440A";
+			public const string KaratekaPAL = "MD5:5E0A1E832BBCEA6FACB832FDE23A440A";
 
-			public const string Serpentine = "md5:9BD70C06D3386F76F8162881699A777A";
+			public const string Serpentine = "MD5:9BD70C06D3386F76F8162881699A777A";
 		}
 
 		// this register selects between 2600 and 7800 mode in the A7800
@@ -120,9 +120,8 @@ namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
 			// look up hash in gamedb to see what mapper to use
 			// if none found default is zero
 			// also check for PAL region
-			string hash_md5 = null;
 			s_mapper = null;
-			hash_md5 = "md5:" + rom.HashMD5(0, rom.Length);
+			var hash_md5 = MD5Checksum.ComputePrefixedHex(rom);
 
 			var gi = Database.CheckDatabase(hash_md5);
 

src/BizHawk.Emulation.Cores/Consoles/GCE/Vectrex/VectrexHawk.cs

@@ -1,6 +1,6 @@
 using System;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.MC6809;
 
@@ -13,7 +13,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Vectrex
 	{
 		internal static class RomChecksums
 		{
-			public const string Minestorm = /*sha1:*/"65D07426B520DDD3115D40F255511E0FD2E20AE7";
+			public const string Minestorm = "SHA1:65D07426B520DDD3115D40F255511E0FD2E20AE7";
 		}
 
 		public byte[] RAM = new byte[0x400];
@@ -57,8 +57,8 @@ namespace BizHawk.Emulation.Cores.Consoles.Vectrex
 			/*var Bios =*/ _bios = comm.CoreFileProvider.GetFirmwareOrThrow(new("VEC", "Bios"), "BIOS Not Found, Cannot Load");
 			/*var Mine =*/ minestorm = comm.CoreFileProvider.GetFirmwareOrThrow(new("VEC", "Minestorm"), "Minestorm Not Found, Cannot Load");
 
-			var romHashSHA1 = rom.HashSHA1();
+			var romHashSHA1 = SHA1Checksum.ComputePrefixedHex(rom);
-			Console.WriteLine($"SHA1:{romHashSHA1}");
+			Console.WriteLine(romHashSHA1);
 
 			_rom = rom;
 

src/BizHawk.Emulation.Cores/Consoles/Intellivision/Cartridge.cs

@@ -1,7 +1,6 @@
 using System;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Emulation.Cores.Intellivision
@@ -40,7 +39,7 @@ namespace BizHawk.Emulation.Cores.Intellivision
 
 			// look up hash in gamedb to see what mapper to use
 			string s_mapper = null;
-			var gi = Database.CheckDatabase($"sha1:{rom.HashSHA1(16, rom.Length - 16)}");
+			var gi = Database.CheckDatabase(SHA1Checksum.ComputePrefixedHex(rom.AsSpan(start: 16, length: rom.Length - 32)));
 			if (gi != null && !gi.GetOptions().TryGetValue("board", out s_mapper)) throw new Exception("INTV gamedb entries must have a board identifier!");
 			_mapper = 0;
 			int.TryParse(s_mapper, out _mapper);

src/BizHawk.Emulation.Cores/Consoles/Magnavox/Odyssey2/O2Hawk.cs

@@ -1,6 +1,6 @@
 using System;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.I8048;
 
@@ -67,8 +67,8 @@ namespace BizHawk.Emulation.Cores.Consoles.O2Hawk
 
 			Buffer.BlockCopy(rom, 0x100, header, 0, 0x50);
 
-			Console.WriteLine("MD5: " + rom.HashMD5(0, rom.Length));
+			Console.WriteLine(MD5Checksum.ComputePrefixedHex(rom));
-			Console.WriteLine("SHA1: " + rom.HashSHA1(0, rom.Length));
+			Console.WriteLine(SHA1Checksum.ComputePrefixedHex(rom));
 			_rom = rom;
 
 			if (game["XROM"]) { is_XROM = true; }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesCore.cs

@@ -3,7 +3,7 @@ using System.Linq;
 using System.Xml;
 using System.IO;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.W65816;
 
@@ -48,7 +48,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 					? CoreComm.CoreFileProvider.GetFirmwareOrThrow(new("SNES", "Rom_SGB2"), "SGB2 Rom is required for SGB2 emulation.")
 					: CoreComm.CoreFileProvider.GetFirmwareOrThrow(new("SNES", "Rom_SGB"), "SGB1 Rom is required for SGB1 emulation.");
 
-				game.FirmwareHash = sgbRomData.HashSHA1();
+				game.FirmwareHash = SHA1Checksum.ComputeDigestHex(sgbRomData);
 			}
 
 			BsnesApi.SnesCallbacks callbacks = new()

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.cs

@@ -1,6 +1,6 @@
 using System;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.LR35902;
 
@@ -26,27 +26,27 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 	{
 		internal static class RomChecksums
 		{
-			public const string BombermanCollection = /*sha1:*/"385F8FAFA53A83F8F65E1E619FE124BBF7DB4A98";
+			public const string BombermanCollection = "SHA1:385F8FAFA53A83F8F65E1E619FE124BBF7DB4A98";
 
-			public const string BombermanSelectionKORNotInGameDB = /*sha1:*/"52451464A9F4DD5FAEFE4594954CBCE03BFF0D05";
+			public const string BombermanSelectionKORNotInGameDB = "SHA1:52451464A9F4DD5FAEFE4594954CBCE03BFF0D05";
 
-			public const string MortalKombatIAndIIUSAEU = /*sha1:*/"E337489255B33367CE26194FC4038346D3388BD9";
+			public const string MortalKombatIAndIIUSAEU = "SHA1:E337489255B33367CE26194FC4038346D3388BD9";
 
-			public const string PirateRockMan8 = /*md5:*/"CAE0998A899DF2EE6ABA8E7695C2A096";
+			public const string PirateRockMan8 = "MD5:CAE0998A899DF2EE6ABA8E7695C2A096";
 
-			public const string PirateSachen1 = /*md5:*/"D3C1924D847BC5D125BF54C2076BE27A";
+			public const string PirateSachen1 = "MD5:D3C1924D847BC5D125BF54C2076BE27A";
 
-			public const string UnknownRomA = /*md5:*/"97122B9B183AAB4079C8D36A4CE6E9C1";
+			public const string UnknownRomA = "MD5:97122B9B183AAB4079C8D36A4CE6E9C1";
 
-			public const string WisdomTreeExodus = /*sha1:*/"685D5A47A1FC386D7B451C8B2733E654B7779B71";
+			public const string WisdomTreeExodus = "SHA1:685D5A47A1FC386D7B451C8B2733E654B7779B71";
 
-			public const string WisdomTreeJoshua = /*sha1:*/"019B4B0E76336E2613AE6E8B415B5C65F6D465A5";
+			public const string WisdomTreeJoshua = "SHA1:019B4B0E76336E2613AE6E8B415B5C65F6D465A5";
 
-			public const string WisdomTreeKJVBible = /*sha1:*/"6362FDE9DCB08242A64F2FBEA33DE93D1776A6E0";
+			public const string WisdomTreeKJVBible = "SHA1:6362FDE9DCB08242A64F2FBEA33DE93D1776A6E0";
 
-			public const string WisdomTreeNIVBible = /*sha1:*/"136CF97A8C3560EC9DB3D8F354D91B7DE27E0743";
+			public const string WisdomTreeNIVBible = "SHA1:136CF97A8C3560EC9DB3D8F354D91B7DE27E0743";
 
-			public const string WisdomTreeSpiritualWarfare = /*sha1:*/"6E6AE5DBD8FF8B8F41B8411EF119E96E4ECF763F";
+			public const string WisdomTreeSpiritualWarfare = "SHA1:6E6AE5DBD8FF8B8F41B8411EF119E96E4ECF763F";
 		}
 
 		// this register controls whether or not the GB BIOS is mapped into memory
@@ -186,10 +186,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				is_GB_in_GBC = true; // for movie files
 			}
 
-			var romHashMD5 = rom.HashMD5();
+			var romHashMD5 = MD5Checksum.ComputePrefixedHex(rom);
-			Console.WriteLine($"MD5: {romHashMD5}");
+			Console.WriteLine(romHashMD5);
-			var romHashSHA1 = rom.HashSHA1();
+			var romHashSHA1 = SHA1Checksum.ComputePrefixedHex(rom);
-			Console.WriteLine($"SHA1: {romHashSHA1}");
+			Console.WriteLine(romHashSHA1);
 			_rom = rom;
 			var mppr = Setup_Mapper(romHashMD5, romHashSHA1);
 			if (cart_RAM != null) { cart_RAM_vbls = new byte[cart_RAM.Length]; }

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.Linq;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Consoles.Nintendo.Gameboy;
 
@@ -137,7 +136,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 
 				InitMemoryDomains();
 
-				RomDetails = $"{game.Name}\r\nSHA1:{file.HashSHA1()}\r\nMD5:{file.HashMD5()}\r\n";
+				RomDetails = $"{game.Name}\r\n{SHA1Checksum.ComputePrefixedHex(file)}\r\n{MD5Checksum.ComputePrefixedHex(file)}\r\n";
 
 				byte[] buff = new byte[32];
 				LibGambatte.gambatte_romtitle(GambatteState, buff);

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NDS/NDSFirmware.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Runtime.InteropServices;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
@@ -192,7 +192,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.NDS
 				byte[] DecryptedFirmware = new byte[decrypedfwlen];
 				Marshal.Copy(decryptedfw, DecryptedFirmware, 0, decrypedfwlen);
 				FreeDecryptedFirmware(decryptedfw);
-				var hash = BufferExtensions.HashSHA1(DecryptedFirmware, 0, decrypedfwlen);
+				var hash = SHA1Checksum.ComputeDigestHex(DecryptedFirmware);
 				if (hash != goodhashes[0] && hash != goodhashes[1] && hash != goodhashes[2])
 				{
 					comm.ShowMessage("Potentially bad firmware dump! Decrypted hash " + hash + " does not match known good dumps.");

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/BootGodDB.cs

@@ -135,7 +135,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 						{
 							currCart = new CartInfo();
 							currCart.System = xmlReader.GetAttribute("system");
-							currCart.Sha1 = "sha1:" + xmlReader.GetAttribute("sha1");
+							currCart.Sha1 = $"SHA1:{xmlReader.GetAttribute("sha1")}";
 							currCart.Name = currName;
 							state = 2;
 						}

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/NES.Core.cs

@@ -23,7 +23,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 			public const string DancingBlocks = /*sha1:*/"68ABE1E49C9E9CCEA978A48232432C252E5912C0";
 
-			public const string SeicrossRev2 = "sha1:4C9C05FAD6F6F33A92A27C2EDC1E7DE12D7F216D"; // yes this is meant to include the prefix
+			public const string SeicrossRev2 = "SHA1:4C9C05FAD6F6F33A92A27C2EDC1E7DE12D7F216D"; // yes this is meant to include the prefix
 
 			public const string SilvaSaga = /*sha1:*/"00C50062A2DECE99580063777590F26A253AAB6B";
 
@@ -258,23 +258,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 			// some boards cannot have specific values in RAM upon initialization
 			// Let's hard code those cases here
 			// these will be defined through the gameDB exclusively for now.
-			if (cart.GameInfo != null)
+			var hash = cart.GameInfo?.Hash; // SHA1 or MD5 (see NES.IdentifyFromGameDB)
+			if (hash is null)
 			{
-				if (cart.GameInfo.Hash is RomChecksums.CamericaGolden5 or RomChecksums.CamericaGolden5Overdump or RomChecksums.CamericaPegasus4in1)
+				// short-circuit
+			}
+			else if (hash is RomChecksums.CamericaGolden5 or RomChecksums.CamericaGolden5Overdump or RomChecksums.CamericaPegasus4in1)
+			{
+				ram[0x701] = 0xFF;
+			}
+			else if (hash == RomChecksums.DancingBlocks)
+			{
+				ram[0xEC] = 0;
+				ram[0xED] = 0;
+			}
+			else if (hash == RomChecksums.SilvaSaga || hash == RomChecksums.Fam_Jump_II)
+			{
+				for (int i = 0; i < Board.Wram.Length; i++)
 				{
-					ram[0x701] = 0xFF;
+					Board.Wram[i] = 0xFF;
-				}
-				else if (cart.GameInfo.Hash == RomChecksums.DancingBlocks)
-				{
-					ram[0xEC] = 0;
-					ram[0xED] = 0;
-				}
-				else if (cart.GameInfo.Hash == RomChecksums.SilvaSaga || cart.GameInfo.Hash == RomChecksums.Fam_Jump_II)
-				{
-					for (int i = 0; i < Board.Wram.Length; i++)
-					{
-						Board.Wram[i] = 0xFF;
-					}
 				}
 			}
 		}

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/NES.cs

@@ -3,7 +3,7 @@ using System.Linq;
 using System.IO;
 using System.Collections.Generic;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 
 //TODO - redo all timekeeping in terms of master clock
@@ -417,11 +417,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 					// we don't have an ines header, check if the game hash is in the game db
 					exists = false;
 					Console.WriteLine("headerless ROM, using Game DB");
-					hash_md5 = "md5:" + file.HashMD5(0, file.Length);
+					hash_md5 = MD5Checksum.ComputePrefixedHex(file);
-					hash_sha1 = "sha1:" + file.HashSHA1(0, file.Length);
+					hash_sha1 = SHA1Checksum.ComputePrefixedHex(file);
-					if (hash_md5 != null) choice = IdentifyFromGameDB(hash_md5);
+					choice = IdentifyFromGameDB(hash_md5) ?? IdentifyFromGameDB(hash_sha1);
-					if (choice == null)
-						choice = IdentifyFromGameDB(hash_sha1);
 					if (choice==null)
 					{
 						hash_sha1_several.Add(hash_sha1);
@@ -443,9 +441,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				{
 					//now that we know we have an iNES header, we can try to ignore it.
 
-					hash_sha1 = "sha1:" + file.HashSHA1(16, file.Length - 16);
+					var trimmed = file.AsSpan(start: 16, length: file.Length - 32);
+					hash_sha1 = SHA1Checksum.ComputePrefixedHex(trimmed);
 					hash_sha1_several.Add(hash_sha1);
-					hash_md5 = "md5:" + file.HashMD5(16, file.Length - 16);
+					hash_md5 = MD5Checksum.ComputePrefixedHex(trimmed);
 
 					LoadWriteLine("Found iNES header:");
 					LoadWriteLine(iNesHeaderInfo.ToString());
@@ -485,10 +484,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 						}
 						msTemp.Flush();
 						var bytes = msTemp.ToArray();
-						var hash = "sha1:" + bytes.HashSHA1(0, bytes.Length);
+						var hash = SHA1Checksum.ComputePrefixedHex(bytes);
 						LoadWriteLine("  PRG (8KB) + CHR hash: {0}", hash);
 						hash_sha1_several.Add(hash);
-						hash = "md5:" + bytes.HashMD5(0, bytes.Length);
+						hash = MD5Checksum.ComputePrefixedHex(bytes);
 						LoadWriteLine("  PRG (8KB) + CHR hash:  {0}", hash);
 					}
 				}

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Unif.cs

@@ -4,6 +4,7 @@ using System.Linq;
 using System.Text;
 using System.IO;
 
+using BizHawk.Common;
 using BizHawk.Common.BufferExtensions;
 using BizHawk.Common.IOExtensions;
 
@@ -95,16 +96,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				Cart.WramBattery = true;
 			}
 
-			// is there any way using System.Security.Cryptography.SHA1 to compute the hash of
+			Cart.Sha1 = SHA1Checksum.ComputeConcat(Prg, Chr).BytesToHexString();
-			// prg concatenated with chr?  i couldn't figure it out, so this implementation is dumb
-			{
-				var ms = new MemoryStream();
-				ms.Write(Prg, 0, Prg.Length);
-				ms.Write(Chr, 0, Chr.Length);
-				ms.Close();
-				var all = ms.ToArray();
-				Cart.Sha1 = "sha1:" + all.HashSHA1(0, all.Length);
-			}
 
 			// other code will expect this
 			if (Chr.Length == 0)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/QuickNES/QuickNES.cs

@@ -9,7 +9,6 @@ using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Nintendo.NES;
 using BizHawk.BizInvoke;
-using BizHawk.Common.BufferExtensions;
 
 namespace BizHawk.Emulation.Cores.Consoles.Nintendo.QuickNES
 {
@@ -245,7 +244,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.QuickNES
 				for (int i = 0; i < chrrom.Size; i++)
 					ms.WriteByte(chrrom.PeekByte(i));
 
-			string sha1 = ms.ToArray().HashSHA1();
+			var sha1 = SHA1Checksum.ComputeDigestHex(ms.ToArray());
 			Console.WriteLine("Hash for BootGod: {0}", sha1);
 
 			// Bail out on ROM's known to not be playable by this core
@@ -300,7 +299,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.QuickNES
 		// we need to do this from the raw file since QuickNES hasn't had time to process it yet.
 		private byte[] FixInesHeader(byte[] file)
 		{
-			string sha1 = BufferExtensions.HashSHA1(file);
+			var sha1 = SHA1Checksum.ComputeDigestHex(file);
 			bool didSomething = false;
 
 			Console.WriteLine(sha1);

src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs

@@ -3,7 +3,7 @@ using System.Linq;
 using System.Xml;
 using System.IO;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components.W65816;
 
@@ -53,7 +53,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 				}
 
 				sgbRomData = CoreComm.CoreFileProvider.GetFirmwareOrThrow(new("SNES", "Rom_SGB"), "SGB Rom is required for SGB emulation.");
-				game.FirmwareHash = sgbRomData.HashSHA1();
+				game.FirmwareHash = SHA1Checksum.ComputeDigestHex(sgbRomData);
 			}
 
 			_settings = (SnesSettings)settings ?? new SnesSettings();

src/BizHawk.Emulation.Cores/Consoles/PC Engine/PCEngine.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Cores.Components;
 using BizHawk.Emulation.Cores.Components.H6280;
@@ -68,7 +68,7 @@ namespace BizHawk.Emulation.Cores.PCEngine
 					throw new Exception();
 				}
 
-				lp.Game.FirmwareHash = rom.HashSHA1();
+				lp.Game.FirmwareHash = SHA1Checksum.ComputeDigestHex(rom);
 
 				Init(lp.Game, rom);
 

src/BizHawk.Emulation.Cores/Consoles/Sony/PSX/Octoshock.cs

@@ -66,7 +66,7 @@ namespace BizHawk.Emulation.Cores.Sony.PSX
 				var sw = new StringWriter();
 				foreach (var d in lp.Discs)
 				{
-					var discHash = new DiscHasher(d.DiscData).Calculate_PSX_BizIDHash().ToString("X8");
+					var discHash = new DiscHasher(d.DiscData).Calculate_PSX_BizIDHash();
 					sw.WriteLine(Path.GetFileName(d.DiscName));
 					sw.WriteLine(DiscHashWarningText(Database.CheckDatabase(discHash), discHash));
 					sw.WriteLine("-------------------------");

src/BizHawk.Emulation.DiscSystem/DiscHasher.cs

@@ -17,7 +17,7 @@ namespace BizHawk.Emulation.DiscSystem
 		/// <summary>
 		/// calculates the hash for quick PSX Disc identification
 		/// </summary>
-		public uint Calculate_PSX_BizIDHash()
+		public string Calculate_PSX_BizIDHash()
 		{
 			//notes about the hash:
 			//"Arc the Lad II (J) 1.0 and 1.1 conflict up to 25 sectors (so use 26)
@@ -54,7 +54,7 @@ namespace BizHawk.Emulation.DiscSystem
 				crc.Add(buffer2352);
 			}
 
-			return crc.Result;
+			return CRC32Checksum.BytesAsDigest(crc.Result).BytesToHexString();
 		}
 
 		/// <summary>
@@ -97,7 +97,7 @@ namespace BizHawk.Emulation.DiscSystem
 				for (int s = 0; s < 512 && s < lba_len; s++)
 					dsr.ReadLBA_2352(track.LBA + s, buffer, s * 2352);
 
-				return buffer.HashMD5(0, lba_len * 2352);
+				return MD5Checksum.ComputeDigestHex(buffer.AsSpan(start: 0, length: lba_len * 2352));
 			}
 			return "no data track found";
 		}

src/BizHawk.Tests/Client.Common/dearchive/DearchivalTests.cs

@@ -3,7 +3,7 @@ using System.IO;
 using System.Linq;
 
 using BizHawk.Client.Common;
-using BizHawk.Common.BufferExtensions;
+using BizHawk.Common;
 using BizHawk.Common.IOExtensions;
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
@@ -29,7 +29,7 @@ namespace BizHawk.Tests.Client.Common.Dearchive
 		private byte[] Rom => _rom.Value;
 
 		[TestMethod]
-		public void SanityCheck() => Assert.AreEqual("70DCA8E791878BDD32426391E4233EA52B47CDD1", Rom.HashSHA1());
+		public void SanityCheck() => Assert.AreEqual("SHA1:70DCA8E791878BDD32426391E4233EA52B47CDD1", SHA1Checksum.ComputePrefixedHex(Rom));
 
 		[TestMethod]
 		public void TestSharpCompress()