现在很多平台开放了api，提供各位开发者使用。一般的open api类似新浪那些，使用时候来个用户授权即可，但是有些平台提供的api，可能连用户授权界面都难以进入，因为这个要求md5加密appkey、time之类的，那个又要求sha1加密。
这里收集了一些加密的方法，利己利人。
//16位MD5加密方式- (NSString *)getMd5_16Bit_String:(NSString *)srcString{ //提取32位MD5散列的中间16位 NSString *md5_32Bit_String=[self getMd5_32Bit_String:srcString]; NSString *result = [[md5_32Bit_String substringToIndex:24] substringFromIndex:8];//即9～25位 return result;}//32位MD5加密方式- (NSString *)getMd5_32Bit_String:(NSString *)srcString{ const char *cStr = [srcString UTF8String]; unsigned char digest[CC_MD5_DIGEST_LENGTH]; CC_MD5( cStr, strlen(cStr), digest ); NSMutableString *result = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2]; for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) [result appendFormat:@"%02x", digest[i]]; return result;}//sha1加密方式- (NSString *)getSha1String:(NSString *)srcString{ const char *cstr = [srcString cStringUsingEncoding:NSUTF8StringEncoding]; NSData *data = [NSData dataWithBytes:cstr length:srcString.length]; uint8_t digest[CC_SHA1_DIGEST_LENGTH]; CC_SHA1(data.bytes, data.length, digest); NSMutableString* result = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2]; for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++) { [result appendFormat:@"%02x", digest[i]]; } return result;}//sha256加密方式- (NSString *)getSha256String:(NSString *)srcString { const char *cstr = [srcString cStringUsingEncoding:NSUTF8StringEncoding]; NSData *data = [NSData dataWithBytes:cstr length:srcString.length]; uint8_t digest[CC_SHA256_DIGEST_LENGTH]; CC_SHA1(data.bytes, data.length, digest); NSMutableString* result = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2]; for(int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) { [result appendFormat:@"%02x", digest[i]]; } return result;}//sha384加密方式- (NSString *)getSha384String:(NSString *)srcString { const char *cstr = [srcString cStringUsingEncoding:NSUTF8StringEncoding]; NSData *data = [NSData dataWithBytes:cstr length:srcString.length]; uint8_t digest[CC_SHA384_DIGEST_LENGTH]; CC_SHA1(data.bytes, data.length, digest); NSMutableString* result = [NSMutableString stringWithCapacity:CC_SHA384_DIGEST_LENGTH * 2]; for(int i = 0; i < CC_SHA384_DIGEST_LENGTH; i++) { [result appendFormat:@"%02x", digest[i]]; } return result;}//sha512加密方式- (NSString*) getSha512String:(NSString*)srcString { const char *cstr = [srcString cStringUsingEncoding:NSUTF8StringEncoding]; NSData *data = [NSData dataWithBytes:cstr length:srcString.length]; uint8_t digest[CC_SHA512_DIGEST_LENGTH]; CC_SHA512(data.bytes, data.length, digest); NSMutableString* result = [NSMutableString stringWithCapacity:CC_SHA512_DIGEST_LENGTH * 2]; for(int i = 0; i < CC_SHA512_DIGEST_LENGTH; i++) [result appendFormat:@"%02x", digest[i]]; return result;}
不过记得在头文件添加一句
#import <CommonCrypto/CommonDigest.h>
另外，有些api它接收的上传数据，可能是需要base64编码的～～在这里也附上之前做的一个项目中的代码片段
#import "NSData+Helper.h"static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";@implementation NSData (Helper)+ (NSData *) dataWithBase64EncodedString: (NSString *)string { // Create a memory buffer containing Base64 encoded string data if (string == nil) [NSException raise:NSInvalidArgumentException format:nil]; if ([string length] == 0) return [NSData data]; static char *decodingTable = NULL; if (decodingTable == NULL) { decodingTable = malloc(256); if (decodingTable == NULL) return nil; memset(decodingTable, CHAR_MAX, 256); NSUInteger i; for (i = 0; i < 64; i++) decodingTable[(short)encodingTable[i]] = i; } const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding]; if (characters == NULL) // Not an ASCII string! return nil; char *bytes = malloc((([string length] + 3) / 4) * 3); if (bytes == NULL) return nil; NSUInteger length = 0; NSUInteger i = 0; while (YES) { char buffer[4]; short bufferLength; for (bufferLength = 0; bufferLength < 4; i++) { if (characters[i] == '\0') break; if (isspace(characters[i]) || characters[i] == '=') continue; buffer[bufferLength] = decodingTable[(short)characters[i]]; if (buffer[bufferLength++] == CHAR_MAX) // Illegal character! { free(bytes); return nil; } } if (bufferLength == 0) break; if (bufferLength == 1) // At least two characters are needed to produce one byte! { free(bytes); return nil; } // Decode the characters in the buffer to bytes. bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4); if (bufferLength > 2) bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2); if (bufferLength > 3) bytes[length++] = (buffer[2] << 6) | buffer[3]; } realloc(bytes, length); return [NSData dataWithBytesNoCopy:bytes length:length];}- (NSString *)base64Encoding;{ if ([self length] == 0) return @""; char *characters = malloc((([self length] + 2) / 3) * 4); if (characters == NULL) return nil; NSUInteger length = 0; NSUInteger i = 0; while (i < [self length]) { char buffer[3] = { 0,0,0}; short bufferLength = 0; while (bufferLength < 3 && i < [self length]) buffer[bufferLength++] = ((char *)[self bytes])[i++]; // Encode the bytes in the buffer to four characters, including padding "=" characters if necessary. characters[length++] = encodingTable[(buffer[0] & 0xFC) >> 2]; characters[length++] = encodingTable[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)]; if (bufferLength > 1) characters[length++] = encodingTable[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)]; else characters[length++] = '='; if (bufferLength > 2) characters[length++] = encodingTable[buffer[2] & 0x3F]; else characters[length++] = '='; } return [[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES];}@end