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77 lines
2.8 KiB
C#
77 lines
2.8 KiB
C#
// -----------------------------------------------------------------------
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// <copyright file="PasswordLengthSlider.cs" company="aliasvault">
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// Copyright (c) aliasvault. All rights reserved.
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// Licensed under the AGPLv3 license. See LICENSE.md file in the project root for full license information.
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// </copyright>
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// -----------------------------------------------------------------------
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namespace AliasVault.Client.Main.Utilities;
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/// <summary>
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/// Utility functions for password length slider with non-linear scaling.
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///
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/// The slider uses a power curve to provide fine-grained control at lower values
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/// (where most users operate, e.g., 12-32 chars) and coarser control at higher values
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/// (64-256 chars).
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///
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/// This makes it easy to select common password lengths while still allowing
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/// very long passwords when needed.
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/// </summary>
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public static class PasswordLengthSlider
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{
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/// <summary>
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/// Minimum password length.
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/// </summary>
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public const int MinPasswordLength = 8;
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/// <summary>
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/// Maximum password length.
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/// </summary>
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public const int MaxPasswordLength = 256;
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/// <summary>
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/// Slider minimum value (internal representation).
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/// </summary>
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public const double SliderMin = 0;
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/// <summary>
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/// Slider maximum value (internal representation).
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/// </summary>
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public const double SliderMax = 100;
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/// <summary>
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/// Exponent for the power curve.
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/// Higher values = more precision at lower lengths.
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/// 2.0 gives a good balance where ~50% slider = ~70 chars.
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/// </summary>
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private const double Exponent = 2.0;
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/// <summary>
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/// Convert a slider position (0-100) to an actual password length (8-256).
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/// Uses a power curve for non-linear scaling.
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/// </summary>
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/// <param name="sliderValue">The slider position (0-100).</param>
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/// <returns>The password length (8-256).</returns>
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public static int SliderToLength(double sliderValue)
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{
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var normalized = Math.Max(0, Math.Min(1, sliderValue / SliderMax));
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var curved = Math.Pow(normalized, Exponent);
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var length = MinPasswordLength + (curved * (MaxPasswordLength - MinPasswordLength));
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return (int)Math.Round(length);
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}
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/// <summary>
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/// Convert a password length (8-256) to a slider position (0-100).
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/// Inverse of SliderToLength.
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/// </summary>
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/// <param name="length">The password length (8-256).</param>
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/// <returns>The slider position (0-100).</returns>
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public static double LengthToSlider(int length)
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{
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var clampedLength = Math.Max(MinPasswordLength, Math.Min(MaxPasswordLength, length));
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var normalized = (double)(clampedLength - MinPasswordLength) / (MaxPasswordLength - MinPasswordLength);
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var curved = Math.Pow(normalized, 1.0 / Exponent);
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return curved * SliderMax;
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}
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}
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