1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Cryptographic API 4 * 5 * ARC4 Cipher Algorithm 6 * 7 * Jon Oberheide <jon@oberheide.org> 8 */ 9 10 #include <crypto/arc4.h> 11 #include <linux/module.h> 12 13 int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len) 14 { 15 int i, j = 0, k = 0; 16 17 ctx->x = 1; 18 ctx->y = 0; 19 20 for (i = 0; i < 256; i++) 21 ctx->S[i] = i; 22 23 for (i = 0; i < 256; i++) { 24 u32 a = ctx->S[i]; 25 26 j = (j + in_key[k] + a) & 0xff; 27 ctx->S[i] = ctx->S[j]; 28 ctx->S[j] = a; 29 if (++k >= key_len) 30 k = 0; 31 } 32 33 return 0; 34 } 35 EXPORT_SYMBOL(arc4_setkey); 36 37 void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len) 38 { 39 u32 *const S = ctx->S; 40 u32 x, y, a, b; 41 u32 ty, ta, tb; 42 43 if (len == 0) 44 return; 45 46 x = ctx->x; 47 y = ctx->y; 48 49 a = S[x]; 50 y = (y + a) & 0xff; 51 b = S[y]; 52 53 do { 54 S[y] = a; 55 a = (a + b) & 0xff; 56 S[x] = b; 57 x = (x + 1) & 0xff; 58 ta = S[x]; 59 ty = (y + ta) & 0xff; 60 tb = S[ty]; 61 *out++ = *in++ ^ S[a]; 62 if (--len == 0) 63 break; 64 y = ty; 65 a = ta; 66 b = tb; 67 } while (true); 68 69 ctx->x = x; 70 ctx->y = y; 71 } 72 EXPORT_SYMBOL(arc4_crypt); 73 74 MODULE_LICENSE("GPL"); 75